Police are urging people who make their way into Glasgow city centre over the Clyde Street suspension bridge to come forward.
Detectives believe they may have vital information about the death of 41-year-old Scott McGuire.
As revealed by the Evening Times, officers are probing whether Mr McGuire sustained injuries before he was found in the River Clyde July 8.
Detective Inspector Martin Fergus, who is leading the inquiry, said: "I would like to thank those members of the public who have already contacted police.
"But I would like to speak to anyone who passed the suspension bridge between 5.30am and 8.30am on July 8 to contact me on 101."
Officers from Police Scotland's Major Investments Team have already traced several witness.
Detectives are also looking into a report of a fire under the bridge the same day.
Despite a post mortem examination, Mr McGuire's death is being treated as "unexplained" and police are to carry out further forensic examinations.
DI Fergus added: "We are trying to piece together the last movements of Scott, and our inquiries are progressing.
"Our inquiries have revealed that Scott had been sleeping rough near to where his body was discovered, near to Carlton Place."
Anyone with information should call police on 101.