A man has been arrested on suspicion of murder after a 45-year-old woman went missing in Lancashire two months ago.
Susan Waring was last seen at a doctor's surgery in her home town of Darwen on 16 January.
Lancashire Police have arrested a 45-year-old man and are searching a property in Blackburn Road.
Ms Waring's body has not been found, but police said it was "very unusual" that she had not been in contact with friends and family for weeks.
Detective Chief Inspector Geoff Hurst said: "Susan's disappearance has now progressed into a murder investigation and I have a team of detectives working hard to find out what has happened to her and where she may be.
"She is often in touch with her sister and is an active Facebook user but has not logged on since towards the end of January."
He added that anyone who may have information about her disappearance or saw her in the days beforehand should get in touch with detectives.
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"Similarly, if you know anything at all you think could help, please let us know," he said.
Investigators ruled out previous reported sightings of Ms Waring in Dumbarton, West Dunbartonshire.
She is described as being 5ft 5in, of small build, with brown eyes and collar-length, curly brown hair.
She has tattoos on both arms and legs – including smiley faces on her legs – and speaks with a north-west accent.
Anyone with information should call 101 quoting incident reference LC-20190320-0963, or alternatively contact independent charity Crimestoppers anonymously on 0800 555111 or online at crimestoppers-uk.org.