SENDAI (Kyodo) An associate professor at Tohoku University was guilty of "grave negligence" that led a graduate student to commit suicide last August after his doctoral thesis was rejected, university officials said Wednesday.

The 52-year-old associate professor at the graduate school of science, who resigned from his post in late April, rejected the thesis by the 29-year-old student in December 2007 without sufficiently consulting with him, they said, adding the instructor rejected the student's thesis after having instructed him in 2006 not to submit it that year.

The associate professor also did not offer concrete instructions on when the student had to rewrite a separate thesis for a magazine, according to the officials.

After the student killed himself in Shiga Prefecture, his parents questioned the assistant professor's guidance, prompting the university to launch an in-house probe.