Hundreds of children were evacuated from Pleasant Hill Elementary Monday afternoon after a pipe bomb was found on the campus, marking the second recent discovery of an explosive device in the usually quiet suburb.

Police were trying to determine if the two cases are connected.

The pipe bomb was spotted in the bushes near the office at Pleasant Hill Elementary around 1 p.m.

"Right outside a window," said Pleasant Hill Police Lt. Dan Connelly. "Had it gone off it would have created some damage to the school, absolutely."

600 students plus faculty and staff were evacuated from the campus on oak park boulevard and taken to a church next door where the parents picked their kids up.

The Walnut Creek police bomb squad was called in to check the device.

"[They] found that it did contain an explosive substance inside and it was a live explosive device," said Connelly.

No one was injured.

Authorities are looking for clues that might link this explosive to a pipe bomb that blew up inside a metal mail box on Christine Court last Friday night.

Police tracked down a Red Chevy Blazer that was seen fleeing the area to College Park High School and detained five teenagers after finding another explosive device.

Two of those teens were arrested.

"We have some good leads. We have some good video we're hoping to examine and determine one way or the other whether or not they're involved in other crimes.

Residents KTVU spoke with were surprised at the recent incidents.

"It is frightening and I just heard it before coming here, so I'm still processing it," said area resident Eleanor Clark. "It does seem out of place."

Nicole Becker just moved to Pleasant Hill from San Francisco.

"[It's a] little, small quaint town. the burbs. something nice. quiet. So it's a little scary knowing that something's going on," said Becker.

Police said they will be reviewing school security cameras to see if the culprit was recorded placing the explosive on campus.

Authorities also said they may be able to get fingerprints from the device found, which could lead them to their bomb maker.