Police are investigating whether the family of Tokyo's 'oldest man' - who appears to have been dead at home for decades - fraudulently received pension money paid to him, news reports said Friday.

City officials went to see Sogen Kato, listed as Tokyo's oldest man, to congratulate him on his 111th birthday, but discovered he had been dead for 30 years.

Officials had long tried to meet Kato, born July 22, 1899, but his family members would not let them in, saying Kato did not want to see anyone or that he was in Gifu Prefecture, news reports said.

Authorities became suspicious and sought police help. On Wednesday, officers forced their way into the house and found the mummified body in bed.

An autopsy Thursday could not identify the cause or time of Kato's death, but since no newspapers newer than one dated Nov 5, 1978, were found in the room and based on his family's account, he most likely died around that time, Kyodo News reported citing unnamed sources.

Kato's relatives told police he had holed up in his room about 30 years ago as he wanted to be 'a living Buddha', news reports said.

Some 6.1 million yen ($70,500) had been already withdrawn from a total of 9.5 million yen paid to Kato as a pension, the Nikkei business daily reported Friday.