A bomb threat ? the fourth one this year ? forced the evacuation of Irvington Middle-High School students Tuesday.

The assistant principal called police to the school off N. Broadway about 9:18 a.m. after receiving a phone threat. Police, the county bomb squad and K-9 units swept the campus. Authorities say they did not find any explosives, but did detonate an item around 10:30 a.m. they found at the school.

Parents are worried about the constant threats. "My biggest concern is that when there is actually an emergency it won't be taken seriously," Sasha Wilson said. "I'm also a little bit concerned about how much school they've been missing."Police have not made any arrests in the incident.

For interviews about the bomb scare, go to channel 612 on your digital iO cable box and select iO Extra.