Prosecutors plan to question accountants and other staffers related to a fundraising body for trade minister Toshihiro Nikai as they widen their probe into illicit political donations to include Prime Minister Taro Aso's Cabinet, sources said Saturday.

An expanded team of nearly a dozen prosecutors is expected to begin questioning Nikai's associates within the week. They suspect Nikai's staff was aware that accepting money for fundraising tickets bought by two political organizations linked to Nishimatsu Construction Co., and other donations allegedly made by the contractor, were illegal, they said.

The move by the Tokyo District Public Prosecutor's Office is based on accounts by former Nishimatsu President Mikio Kunisawa, who has been arrested for breaking the political funds control law, the sources said.