Police questioned an Osaka Dental University professor late last year over his involvement in leaking questions on the March 2000 National Dentistry Examination, investigative sources said Thursday.

They said the unidentified 62-year-old teacher was an exam board member and friend of former Ohu University professor Kenji Kusunoki, who was arrested Saturday for allegedly leaking questions on the test to his students.

The Metropolitan Police Department suspects the Osaka teacher provided Kusunoki with exam questions as the latter told the health ministry in August last year that the teacher gave him keywords relating to the exam, the sources said.

They said the Osaka professor told the police that he had spoken to Kusunoki over the phone, but denied being involved in the leaks.

Kusunoki and the professor are both graduates of Osaka Dental University in Hirakata, Osaka Prefecture, and have been friends since college, the sources said, adding that the two often chatted over the phone and dined together.

Kusunoki, 54, resigned from Ohu, a private university in Fukushima Prefecture, in September.

The professor, who concurrently serves as head of the Osaka Dental University Hospital in Osaka's Chuo Ward, became an exam board member in 1999, according to the sources.

The ministry -- now known as the Health, Labor and Welfare Ministry -- requested in August that he not attend board meetings following rumors he was involved in leaks of national exam questions.

He was one of the board members responsible for drafting questions on subjects other than oral hygiene for exams held in 1999 and last year.

Itsuo Ueda, a 59-year-old professor with the Health Sciences University of Hokkaido who served on the board between July 1998 and June 2000, was also arrested Saturday on charges of providing questions to Kusunoki.

Ueda was responsible for drawing up the oral hygiene questions.