An imprisoned mobster on trial for manslaughter in Chiba phoned the family of a former deputy mayor also behind bars and swindled them out of 13 million yen last spring by having them deposit the money into an account ostensibly for bail, police said Tuesday.

Hiroyuki Kuwabara, 32, is suspected of obtaining a cellular phone from a guard in the Chiba prison and tricking the family of Akira Kawai, former deputy mayor of Kamagaya in Chiba Prefecture, into transferring the sum into the account after identifying himself as an employee of a law firm.

Kawai, 60, was arrested for allegedly accepting bribes from a construction company via an aide to former House of Councilors President Yutaka Inoue. He is in the same prison as Kuwabara, who bilked the family out of the money sometime around last spring, they said.

Kuwabara is on trial for allegedly killing a gangster in September 1999 in Chiba.

Prison officials said the guard may have violated rules, but that they will await the results of a police investigation before deciding on any punishment.

Starting in December 2000, Kuwabara and four fellow mobster inmates had the prison guard secretly bring them food, according to police.

Police said Kuwabara later threatened the guard and quoted him as saying: "You're breaking the law. We're going to tell your boss." Police also alleged that he blackmailed the guard and received 6.3 million yen between last May and June.

Kuwabara was served an arrest warrant for blackmail earlier this month.