An emergency operation was initiated last night in Strabane after a male entered the River Mourne.
The PSNI in Strabane are now appealing for information in relation to the man who was extracted from the river at approximately 7.15pm yesterday evening.
A number of local volunteer groups as well as Northern Ireland Fire and Rescue service and the Ambulance Service were at the secene and carrying out seaches into the early hours of this morning.
Police are becoming increasingly concerned as to the man's whereabouts after he subsequently disappeared from the area.
The man was assisted to the shore just downstream of the Strabane footbridge, on the Ballycolman side of the river.
He is described as having closely-cut fair hair, wearing a white t-shirt, jeans and slippers, and is possibly of Eastern European origin.
This man left the locality before any further assistance arrived to ascertain his well-being.
At this time, Police have been unable to trace the individual involved and would ask that he make contact with Police as soon as possible to confirm his welfare.