COLUMBIA, Mo. -- A student at the University of Columbia has been charged with using another student's e-mail account to send thousands of junk e-mails soliciting traffic for adult-themed Web sites.

Boone County prosecutors charged Matthew J. Graves, 22, with three counts of computer tampering. His arrest on Wednesday followed an investigation by university police and the school's office of Information & Access Technology Services.

The investigation began in early February, police Maj. Doug Schwandt said, when school officials reported unusual activities -- dating back to October -- on the e-mail account of the alleged victim.

Employees first froze the account of the alleged victim and had campus police contact that student, said Todd Krupa, spokesman for the school's office of Information & Access Technology Services.

Shortly thereafter, however, Krupa said employees noticed similar activity on Graves' account, prompting them to believe he also was a victim of an unknown third party.

But after Graves and his victim were given new passwords, which should have ended any outside use of their accounts, the activity continued on Graves' account, Krupa said.