KYOTO (Kyodo) A 19-year-old preparatory school student under arrest for allegedly soliciting answers online during the Kyoto University entrance exam has admitted making similar cheating attempts during the tests for three prominent private universities, investigative sources said Friday.

The student from Sendai, whose name is being withheld because he is a minor, said he posted questions from the exams for Waseda, Doshisha and Rikkyo universities using a cell phone while he was taking the tests in February, the sources said. He said he acted alone and used a method similar to the one he used to cheat on theKyoto University entrance exam later that month, they said.

The revelation that he posted the test questions by himself surprised many in Japan because some were long math questions that were posted in a matter of minutes to Yahoo Japan's Chiebukuro (Pearls of Wisdom) question-and-answer service.

The police will examine his mobile phone to see if it has a scanning function that can digitize photographed words and thus facilitate the postings.

While mobile phones are usually designed to make a sound when photographs are taken to alert people in the vicinity, the scanning function in some models doesn't activate any sounds.

The student graduated from a Yamagata high school last March. Police tracked him down Thursday in Sendai after homing in on his mobile phone's GPS signal.