A man whose body was found by the side of railway tracks on Teesside died of hypothermia, a post-mortem examination has revealed.
Detectives are treating the death of 36-year-old Michael Swift, from Hartlepool, as unexplained.
Mr Swift's body was discovered by a member of the public near to Seaton Carew station on 14 December.
British Transport Police (BTP) said efforts were being made to establish Mr Swift's last movements.
Det Insp Stuart Mellish, of BTP, said: "We are currently working to piece together Michael's movements prior to his death.
"It's crucial that anyone who has had contact with him over the last few weeks contacts police as we believe they will be able to help us in our investigation."
A post-mortem examination carried out on Wednesday revealed the cause of death as hypothermia, however Mr Mellish said inquiries were continuing to establish the full circumstances leading up to Mr Swift's death, including how he came to be by the tracks.
He added: "We have released a picture of Michael in the hope that anyone who may have seen him in the last few weeks might recognise him and come forward."