The mother of a missing RAF serviceman has said a third party may have been involved in her son's disappearance.
Corrie McKeague, 23, vanished more than a fortnight ago after going out for the evening with friends in Bury St Edmunds, Suffolk.
Police have searched along a section of railway line and A-roads, hours of CCTV have been reviewed and police officers, RAF personnel and the National Police Air Service helicopter have been trawling the area.
Mr McKeague's mother, Nicola Urquhart, of Dunfermline, Scotland, wrote in a Facebook post: "Police are confident Corrie is not still in Bury and has not left on foot.
"This can only mean there is third party involvement, there is just no evidence so far to prove criminality.
"As such I would ask people to help me find this evidence as someone does know something."
Officers had earlier searched a bin lorry, believing Mr McKeague's mobile phone had been lost or discarded and ended up with the rubbish, but it could not be found.
Mr McKeague, based at RAF Honington, was last seen on CCTV at about 3.20am on Saturday September 24.
He was walking alone, eating fast food, in Bury St Edmunds.
Police issued a further appeal for information over the weekend and said they had traced three witnesses they had been looking to speak to.
Officers searching for Mr McKeague carried out checks in the centre of Bury St Edmunds in the early hours of Saturday, a fortnight after the serviceman's disappearance.
A Suffolk Police spokesman said a number of people were spoken to and information was being reviewed to identify possible new lines of inquiry.
Mr McKeague is believed to have been wearing a pink Ralph Lauren polo shirt and brown suede Timberland boots at the time of his disappearance.
He is described as white, 5ft 10in and of medium build, with short light brown hair.