London, England (CNN) -- A man who worked for a British intelligence agency and was found dead in London this week was seen alive much later than investigators earlier thought, police said Saturday.
London's Metropolitan Police initially said they thought Gareth Williams,30, had been dead for two weeks before his body was found in his apartment Monday. They now believe he was last seen alive August 15.
It is one of the few details police have released about the case. Police said they still don't know the cause or circumstances surrounding Williams' death.
British media reported Williams' body was found stuffed in a bag in the bathroom of his apartment with no obvious signs of foul play.
Williams' family released a statement Friday calling him a "generous, loving son, brother and friend" who loved cycling and music.
"His loss has devastated us and we would ask that anyone with information ... come forward and assist the police enquiry," the statement read. "The continued speculation in the press about his private life has been very distressing."
Williams worked at Government Communications Headquarters (GCHQ), Britain's intelligence agency for monitoring communication and keeping government data secret, the agency told CNN. He was widely reported to have been on loan to MI6, the foreign intelligence service, in London.
Police said they are treating Williams' death as "suspicious and unexplained," and they appealed for anyone with information about Williams' final days to contact them.