A man from Northern Ireland is one of two people being questioned as police re-examine three murders in England 11 years ago.
The 46-year-old was arrested in connection with the murder of a 70-year-old woman strangled and burned in her flat in Hastings in January 1998.
He has since been released on police bail and Sussex Police have not released any further details about his identity.
The bodies of Clare Letchford (40) and Beryl O’Connor (pictured below), known as Dornie, were discovered in their homes less than 100 yards apart.
Now Sussex Police have reopened the case and are linking the deaths to an attempted murder that happened the same month.
Four people were arrested at the time of the attacks but no charges were brought.
Their inquest heard the killer strangled Mrs O'Connor and attempted to strangle Mrs Letchford before setting their bodies on fire.
Mrs Letchford was found dead at her flat on January 18, 1998. Mrs O'Connor was discovered at her home eight days later.
Home Office pathologist Iain West said Mrs Letchford was found badly burned with a pair of shoelaces tied around her neck and a cushion cover over her head. He said she had been restrained before being set alight and died from inhaling smoke.
The attempted murder, which is being investigated by British Transport Police, involves a sex attack on a 19-year-old Czech student on a Hastings to London train.
Police said the investigation into the murders was complex and wide-ranging but that the Crown Prosecution Service would be passed details of their “significant progress” shortly.
Detective Chief Inspector Trevor Bowles of Sussex Police said yesterday: “This investigation is over 11 years old but it still resonates in the thoughts and concerns of the people in Hastings.”
"The re-investigation of the murders of Claire and Dornie is complex and wide-ranging. We will shortly be speaking with the Crown Prosecution Service about the significant and exciting progress we have made."
The attack on the Czech student happened on January 26, 1998, when she was raped and viciously attacked in a toilet just three months after she arrived in East Sussex as an English language student.
Detective Chief Inspector Alistair Cumming, of the BTP, said: "Despite the passage of time, the resolve of British Transport Police to detect this dreadful attack on an innocent train passenger has never diminished.
"It is comforting to the Czech victim that the matter is now being passed to the Crown Prosecution Service."
All three cases featured on the BBC's Crimewatch programme.
The Czech victim, who has since returned to her homeland, was found by a train guard, covered in blood and with severe head injuries, and is said to still suffer as a result of the ordeal.