Gardaí investigating the disappearance of Sandra Collins in the Killala area of Co Mayo 11 years ago arrested a man in his 40s in the Ballina area this morning.
He is being held under Section 4 of the Criminal Justice Act 1984 at Ballina Garda station.
Ms Collins was last seen on the night of Monday, December 4th, 2000, in the seaside village of Killala where she lived when she left her aunt's house to go to the shops.
About three hours later, at 11pm, she was served in a local fast food outlet where she bought two bags of chips. She was never seen again.
Her fleece jacket was later found on the pier in Killala four days later.
When her jacket was discovered, some of the items she had bought in the shops were in the pockets.
Gardaí and the missing woman's family do not believe she was suicidal. An extensive search of the sea around Killala took place and it came to nothing.
Gardaí now believe Ms Collins met someone after going shopping and was still with that person when she went to buy the two portions of chips.
They believe she was killed that night, most likely by the unidentified person she met, and her body was disposed of.
On the 10th anniversary of her disappearance, a fresh appeal to the public was made for any information. A reconstruction of Ms Collins’s last movements was also broadcast.
Since then, gardaí have been contacted with information, some of it concerning a white van that was seen in Killala on the night Ms Collins disappeared.
A man was questioned by gardaí in connection with case but released without charge last March.
A 21-year-old woman was also arrested last March in connection with the case. She would have been aged 11 at the time Ms Collins disappeared and is not suspected of any involvement.
However, she was arrested on suspicion of withholding information on the basis of her friendship with a man in his 40s, who is a suspect. She was also released without charge.
Two other men, aged 47 and 58, were also arrested in March. They were released without charge.