More details have come to light about a man believed to be a member of a Japanese extremist group who remained on the run for almost half a century.

Investigators told NHK that they confirmed that the man believed to be Kirishima Satoshi worked at a civil engineering company in Kanagawa Prefecture, near Tokyo, until he was admitted to a hospital recently.

The man is said to be hospitalized under a false name, and receiving treatment for terminal-stage cancer. He was placed under police custody on Thursday.

Police say an employee of the company was with the man when he was admitted to the hospital, and the employer was not aware that the man may have been the fugitive.

Kirishima is a member of the East Asia Anti-Japan Armed Front. The group is held responsible for 12 bombing attacks in 1974 and 1975, targeting companies doing business abroad.

He was placed on a nationwide wanted list for his suspected involvement in one of the attacks in Tokyo's Ginza district in 1975.

Investigators are trying to confirm the man's identify through DNA analysis and are looking into how he has lived all these years.