Police investigating a body washed up on a North Cornwall beach say they are now treating the death as suspicious.
Officers from the major crime investigation unit made the announcement after a post mortem revealed injuries "which could not be explained".
Police are exploring the possibility the man could have previously been on a boat or ship in the area.
The man's naked body was found on the beach at Perranporth near the Watering Hole pub on Tuesday at approximately 2pm.
Detective Chief Inspector Dave Thorne said: "We are now treating the discovery of the body as suspicious.
"The change in tack has come about as a result of the post mortem held yesterday.
"There are injuries on his body that we are not able to explain, and as a result of that we are treating the death as suspicious."
The police are yet to identify the man, who is thought to be between 50 and 70 years old, with a bald head and a white beard.
Mr Thorne would not elaborate on the nature of the injuries revealed in a post mortem held yesterday.
He said: "We are not happy that they were caused by natural means or through rock or sand abrasions.
"We can't really avoid the fact there may be a third party involved. They are external injuries over various parts of his body."
Police said they believed the man had been in the water for between 12-24 hours and could have come off a boat or ship.
Mr Thorne said: "It's not possible to say where he went in. If you introduce the idea of boats and ships the possibilities became greater.
"At this stage we really don't know, that's why his identity is key to us."
A full search of the area on the beach and the surrounding clifftops was carried out on Wednesday and Thursday.
Following the search they released photographs of a blue jacket which they said may or may not have been connected to the man.
A wallet was in the jacket pocket which contained a photograph of a young boy from the 1950s with the date of April 13, 1952 on the back.
Police also found a set of keys, including a Citroen car key with a fob in the shape of a hippopotamus.
Anybody with any information is asked to contact the police on 101.