SAN ANTONIO -- A threat posted on a Web site that turned out to be a hoax prompted 85 percent of the Warren High School student body to leave class Monday.

At least one student, maybe more, had been identified as the source of the threats, said North Side Independent School District spokesman Pascual Gonzalez.

"At first, it was a rumor because we couldn't identify the message," Gonzalez said. "Since this morning, we have been able to pull down the messages that one or more Warren students have posted on the Web site."

Gonzalez said those involved will be prosecuted.

The prank, posted on myspace.com, indicated that students were going to bring guns on campus to open fire on the student body, Gonzalez said.

After school administrators first learned of the threat Sunday afternoon, they notified campus police, which had extra officers patrolling campus Monday morning. Teachers were also asked to arrive early to school.

As of 10:30 a.m. Monday, only 400 of 3,000 students remained on campus.

"The kids went to school thinking that they were going to be OK, but they got locked in their classrooms and they were going to sit in class all day watching TV, so we decided to pull them out," said Sylvia Flores, a parent of a Warren High School student. "They weren't feeling safe."

All computers in the school district were blocked from having access to the Web site.

District officials urged parents to monitor computer activities of their children at home.