OSAKA -- The prosecutor arrested Monday on suspicion of fraud owns 16 real estate properties but has not declared at least 5 million yen in rent revenue, informed sources alleged Tuesday.

According to the sources, Osaka district prosecutors are studying this aspect of the case to see whether Tamaki Mitsui, 57, former head of the public security department at the Osaka High Public Prosecutor's Office, violated income tax laws.

Mitsui's properties include homes and condominiums in Osaka, Hyogo, Okayama and Kochi prefectures, the sources said. He was already the owner of at least one condo by around 1988, when he became deputy head prosecutor of the Kochi District Public Prosecutor's Office.