Former Japanese trade minister Isshu Sugawara has been questioned by prosecutors on suspicion that his office offered money and gifts to supporters in violation of the country's election law, sources said Wednesday.

The scandal first came to light after a weekly magazine reported in October last year that Sugawara's secretary had offered condolence money to the bereaved family of a supporter in his Tokyo constituency that month. Sugawara resigned as minister the next day, little more than a month after assuming the post.

The Public Offices Election Law bans politicians from making donations to voters in their home constituencies except for money given in person at ceremonies such as weddings and funerals.

The 58-year-old lawmaker of the ruling Liberal Democratic Party said in a news conference Tuesday that he and his secretary handed out condolence money and gifts worth around ¥300,000 ($2,790) a year between 2017 and 2019. He admitted for the first time since stepping down from his ministerial post that he was aware of the illegality of the acts, saying he wanted to speak in public about the matter before the end of the parliamentary session.

Sugawara said there are several dozen funerals for his supporters each year in his Tokyo constituency. While he gave condolence money in person in most cases, his secretary delivered it when Sugawara was busy or outside the country, he said.

In a separate case involving LDP lawmakers, prosecutors are aiming to establish a case against former Justice Minister Katsuyuki Kawai and his lawmaker wife Anri facing vote buying allegations.