A convicted paedophile wanted by UK police is being investigated in connection with the disappearance of Madeleine McCann.
Briton Raymond Hewlett, was staying near Praia da Luz, in Portugal, when the three-year-old went missing in May 2007, according to reports.
Hewlett, who grew up in Blackpool, Lancashire, has been jailed several times for sexual offences against young girls.
The former soldier, who also lived in Telford, Shropshire, is wanted for questioning by West Yorkshire police in connection with a case dating back more than 30 years.
The Daily Mirror today published a picture of the 64-year-old who, the paper said, was being treated for throat cancer in a German hospital.
Clarence Mitchell, spokesman for Madeleine's parents Kate and Gerry, said Hewlett was being looked at by investigators working for the couple from Rothley in Leicestershire.
He told BBC News: "It's my understanding that if you are on the sexual offenders register you are supposed to alert the authorities to your movements.
"I understand that in this case Mr Hewlett's whereabouts weren't known to a number of police forces for some time.
"Now that he is being treated for an illness in Germany it's up to the individual police forces as to what they do with that information."
He said Madeleine's parents were "fully aware" of the development and added the couple's investigators had been in Portugal for the last week.
A spokeswoman for West Yorkshire Police confirmed they want to speak to Mr Hewlett.
She said: "We are actively seeking him in connection with an indecent assault in 1975."
The alarm was raised about Hewlett by a couple who met him while on holiday in Portugal, the newspaper said.
Alan and Cindy Thompson said Hewlett was living with his wife and six children in a converted Dodge truck travelling from campsite to campsite.
Mr Thompson, 56, told the Mirror Hewlett said he was approached by some "Gipsy tourists" offering to buy his daughter just before Madeleine went missing.
Mrs Thompson, 47, said: "We didn't think too much of this at the time. Ray and his family led a desperate hand-to-mouth lifestyle and someone may have thought he'd be tempted to sell one of his six children."
They also recalled him mentioning a "business" trip to Morocco, where there were several alleged sightings of Madeleine in the months after her disappearance.
Earlier this week, the Thompsons contacted Hewlett to question him about his movements, the Mirror said.
Asked about his Morocco trip, he said: "Yes, so? That makes me guilty then?"
"In Morocco, everything's worth something. You can get 25 euros for an old bike."
Hewlett told the Thompsons he was at a market in the Portuguese town of Fuseta, 30 miles from Praia da Luz, when Madeleine disappeared.
He said: "That place where she was abducted from, I have to have a good memory see, there was a market on that same Sunday.
"We drove there on the Saturday. We were parked there. As I drove out there I saw police going the other way. So it's all very clear for me. I know exactly where I was. I wasn't anywhere near there. Where did you get that I was there?"
Madeleine disappeared on Thursday May 3, 2007.
Hewlett said when he left the market he returned to a campsite in Tavira, where he was staying.
He said: "I do remember where I was that particular weekend. Later I was parked...a mighty long way from where that kid went missing from. If you'd gone in our truck you couldn't have got away with it, driving that about.
"You'd have stood out like a sore thumb."
In September 1972 Hewlett abducted a 12-year-old girl and took her on to moors near his home in Todmorden, West Yorkshire.
He incapacitated her with a rag soaked in paint thinners and she only escaped being raped after he ejaculated prematurely.
In 1978 Hewlett attacked another girl, this time putting a gun to her back but she managed to escape.
He was also questioned over the 1975 murder of 11-year-old Lesley Molseed, following the release of Stefan Kiszko who was wrongly imprisoned for the crime.
Another man, Ronald Castree, was eventually convicted of the girl's murder in 2007.
Hewlett told the Thompsons he had done nothing wrong and they were judging him based on what they knew of his past, the paper reported.
He said: "If you've chosen to believe anything I can't do anything about it anyway, so there you go. Catch 22.
"You're basing it on someone's past, rather. That means the person's past is important. Doesn't make him guilty. You shouldn't be talking to me about it. I've done nothing wrong, nothing, nothing.
"I don't actually believe that child was actually kidnapped, let alone murdered."
KEY EVENTS IN MADELEINE DISAPPEARANCE
:: May 3 - Kate and Gerry McCann, from Rothley, Leicestershire, leave their three children asleep in their holiday apartment in Praia da Luz while they dine with friends at a nearby tapas restaurant.
Nothing is amiss when Mr McCann checks on the youngsters at just after 9pm, but when his wife goes back at about 10pm she finds three-year-old Madeleine missing.
Jane Tanner, one of the friends eating with the McCanns, later reports seeing a man carrying a child away earlier that night.
:: May 5 - Portuguese police reveal they believe Madeleine was abducted but is still alive and in Portugal, and say they have a sketch of a suspect.
:: May 14 - Detectives take Anglo-Portuguese man Robert Murat in for questioning and make him an "arguido", or official suspect.
Officers also search the home he shares with his mother in Praia Da Luz, just 100 yards from where the youngster was snatched.
:: May 25 - Detectives finally release the description of the man reported by Jane Tanner three weeks earlier following pressure from the McCanns, their legal team and the British Government.
:: May 30 - Mr and Mrs McCann meet the Pope in Rome in the first of a series of trips around Europe and beyond to highlight the search for their daughter.
:: August 6 - A Portuguese newspaper reports that British sniffer dogs have found traces of blood on a wall in the McCanns' holiday apartment.
:: August 11 - Exactly 100 days after Madeleine disappeared, investigating officers publicly acknowledge for the first time that she could be dead.
:: August 31 - The McCanns launch a libel action against newspaper Tal and Qual over a front-page story which claimed police believe they killed their daughter.
:: September 7 - During further questioning of Mr and Mrs McCann, detectives make them both "arguidos" in their daughter's disappearance.
:: September 9 - The McCanns fly back to England with their two-year-old twins Sean and Amelie.
:: October 2 - Goncalo Amaral, the detective in charge of the inquiry, is removed from the case after criticising the British police in a Portuguese newspaper interview.
:: October 9 - The case is taken over by Paulo Rebelo, a senior detective with Portugal's investigative Policia Judiciaria normally based in Lisbon.
:: October 25 - The McCanns release a new artist's impression drawn by an FBI-trained expert showing the man described by Jane Tanner.
:: November 1 - Mr McCann returns to work as a consultant cardiologist at Leicester's Glenfield Hospital.
:: December 22 - Mr and Mrs McCann send a public message to their daughter, telling her: "Our only Christmas wish is for you to be back with us again."
:: February 4 - Portugal's top detective, Alipio Ribeiro, says in a radio interview that police were "hasty" in making Madeleine's parents suspects in her disappearance.
:: March 19 - Mr and Mrs McCann accept £550,000 libel damages and front-page apologies from Express Newspapers over allegations they were responsible for Madeleine's death.
:: April 7 - Three Portuguese detectives, led by Mr Rebelo, fly to Britain to re-interview the seven friends on holiday with the McCanns when Madeleine vanished.
:: April 10 - Speaking in Brussels, Mr and Mrs McCann call for a Europe-wide missing child alert system.
But this is overshadowed by a leak of the couple's first police interviews, which reveals that Madeleine asked her mother on the morning before she vanished: "Mummy, why didn't you come when we were crying last night?"
:: April 26 - In an interview for a BBC Radio 4 documentary, Mr McCann says he believes his daughter is still "probably alive" and that there is "absolutely zero" evidence to suggest otherwise.
:: April 30 - An ITV documentary reveals that the McCanns almost decided against leaving their children behind when they went out on the night Madeleine disappeared.
:: May 3 - A tearful Mrs McCann urges people to "pray like mad" for Madeleine as she and her family mark the first anniversary of the little girl's disappearance.
:: July 17 - Mr Murat receives £600,000 in libel damages from four newspaper groups over "seriously defamatory" articles connecting him with the child's disappearance.
:: July 21 - The Portuguese authorities shelve their investigation and lift the "arguido" status of the McCanns and Mr Murat.
:: July 24 - Mr Amaral publishes a book about the case, entitled The Truth Of The Lie, in which he alleges that the young girl died in her family's holiday flat on May 3.
:: August 4 - Thousands of pages of evidence from the Portuguese police files in the exhaustive investigation into Madeleine's disappearance are made public.
They reveal details of the lines of inquiry pursued by detectives, witness statements and scores of previously unknown sightings of the little girl.
:: January 13 - Mr McCann returns to Portugal for the first time since coming back to the UK without his daughter.
:: January 29 - Nearly £2 million was raised for the official fund to find Madeleine in the first 10 months after she went missing, Companies House accounts show.
:: March 24 - The McCanns launch a localised new appeal for information focused on the area in the Algarve where Madeleine disappeared.
:: April 4 - Mr McCann goes back to Portugal to help film a reconstruction of the events on the night his daughter vanished for a new Channel 4 documentary.
:: April 22 - The McCanns fly to the US to record an interview with celebrated chat show host Oprah Winfrey to mark two years since Madeleine's disappearance.
:: May 16 - The McCanns announce they will sue Mr Amaral over comments he made in the media.
:: May 22 - It emerges that British convicted paedophile Raymond Hewlett is being investigated in connection with Madeleine's disappearance.