Tokyo prosecutors have raided the offices of Lower House member Horii Manabu over allegations that he repeatedly made illegal donations.
Investigators entered Horii's offices in Tokyo and Hokkaido on Thursday morning. The lawmaker left the Liberal Democratic Party on the same day.
Sources with knowledge of the matter say Horii, from the proportional representation bloc in Hokkaido, gave condolence money to several people in his constituency about two years ago.
Horii reportedly asked his secretary or a family member to bring condolence money to a wake or funeral that he did not attend.
Under Japan's public office election law, politicians can only give condolence money in their constituency if they attend the funeral service in person and directly hand over the payment.
Horii is also said to have sent funeral flowers in his constituency.
The illegal donations could total thousands of dollars.
Tokyo prosecutors learned of these acts during their investigation into LDP factions' political fundraiser revenues.
Horii allegedly received reports and gave instructions through the Line messaging app on who to give money to and the amounts when he traveled outside Hokkaido.
Horii resigned as State Minister of the Cabinet Office when it was revealed that he had failed to report 21.96 million yen, or about 140,800 dollars, in fundraiser ticket revenue kickbacks from the LDP's Abe faction over a five-year period through 2022.
He is facing criminal complaint on suspicion of violating the political funds control law.