Gardai investigating the case of a woman missing for a decade were last night questioning a woman who was just 11 at the time of her disappearance.
The 21-year-old suspect was being held for questioning last night about withholding information relating to the disappearance of Mayo woman Sandra Collins.
She was arrested at her current address in Ballina, Co Mayo, yesterday morning and taken to the local garda station.
She was being detained last night under Section 30 of the Offences Against the State Act, which allows the gardai to hold her for up to three days.
Sandra Collins (29) was last seen in the Co Mayo town of Killala in the local takeaway, The Country Kitchen, on George's Street, at around 11.15pm on December 4, 2000.
Gardai believe the suspect was in possession of information at that time or since then that could have proved invaluable to their investigation.
Earlier this month, Supt Peter O'Boyle, who is in charge of the renewed investigation of the case, disclosed that a substantial number of new witnesses had emerged after recent public appeals.
Fresh information indicated that a white van was spotted in the town around the time Ms Collins was last seen.
"As a result of our inquiries in the past few months, we are now moving in a certain direction", he told the Irish Independent last night.
He said gardai believed a number of people had intimate knowledge of what took place.
Gardai have appealed to those people to contact Ballina station, at 096 20560, or via the confidential line, 1800 666111.
In 2004, a man who was well known to Ms Collins was detained -- also on suspicion of withholding information. But he was released without charge.
Officers emphasised that they were examining a range of reasons Ms Collins went missing.
Her sister, Bridie Conway, said: "We believe she is dead, unfortunately. The most important thing for us is to get her back.
"Our lives have been on hold to a certain extent for the last 10 years. There is someone out there who could end it all, someone out there with information on what happened to her and where she is.
"We hope at some stage to get her back and we will try to move on ourselves then."
She thanked all who came forward and asked people with information to contact gardai.