Sources say former agriculture minister Yoshikawa Takamori has admitted receiving cash from a former corporate executive while in office. He occupied the post from October 2018 to September of last year.
Yoshikawa, of the Liberal Democratic Party, faces allegations of receiving cash totaling 5 million yen, or about 48,000 dollars, from the former head of a major egg producer based in Fukuyama City in Hiroshima Prefecture.
The former head had been lobbying Diet members and the agriculture ministry over international standards for poultry breeding and other matters. The former head had met with Yoshikawa several times.
Tokyo prosecutors are questioning the former head and ministry officials, as well as Yoshikawa himself, on a voluntary basis.
Sources have told NHK that Yoshikawa admitted receiving cash from the former head earlier this month. They say the ex-minister told people close to him that he wants to provide all the facts if asked by prosecutors for an explanation.
Yoshikawa resigned as a member of the Lower House on Tuesday. He said he is being treated in hospital for a heart illness and is scheduled to undergo surgery.