A 56-year-old professor at Nippon Dental University was arrested Sunday on suspicion of leaking questions on a national dentistry examination last year, bringing the number of those jailed in the scandal to three, police sources said.

Motoo Niwa is suspected of faxing three questions on oral hygiene to Itsuo Ueda, a professor at Health Sciences University of Hokkaido in November 1999, the sources said.

Ueda, 59, is suspected of leaking the information to Kenji Kusunoki, 54-year-old former professor at Ohu University in Koriyama, Fukushima Prefecture, who allegedly leaked the questions to students at Ohu by including them in a graduation exam given Feb. 17 and 18 last year, the sources said.