(May 10, 2007)--Boulder High School in Boulder, Colo. was put on lockdown and then classes were canceled Thursday morning after a school cafeteria worker saw two men in camouflage and masks on the campus.

The worker shouted, and the men ran, police said.

Police were called and a SWAT team was dispatched to sweep the school.

Arriving students gathered off the campus and were told that classes wouldn’t be held.

Boulder police officials told reporters Thursday morning they don’t know whether the men are in the school building, but said they’ve cleared two floors of the multi-story school.

A bomb-sniffing dog was also dispatched to the school.

Police said they would take every precaution they can to ensure students’ safety.

"You really can't take any chances these days,” said Boulder Police Chief Mark Beckner.

“Unfortunately that's the world we live in right now. And we are doing whatever we can to take whatever precautions we can. We want to make sure it's safe and that we're satisfied it's safe before we say OK you can open up the school."

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