Exploding Pens Cause Injuries in L.A.

Booby-trapped pens have exploded and injured three people at Los Angeles area high schools, causing minor burns and scratches on their hands and faces.

The pens were found lying on the ground and blew up when people pulled off their caps.

The most recent case was Friday, when a marker pen exploded in a boy's hands at El Monte High School.

Detective Gary Spencer of the Los Angeles County Sheriff's bomb squad believes the devices are homemade.

"I wouldn't say it's a trick -- people are getting injured," said Spencer. "Whether they're doing it for mischief or they intend to injure people, that's something to be determined."

School administrators have warned students about picking up objects, said El Monte High Principal Joel Kyne.

"You never think it's going to happen to you, ever," he said. "It makes you be aware of the funky things going on."

The first small explosion happened Aug. 24, injuring a construction worker at Rosemead High School. A woman was injured three weeks later by a pen she picked up outside that school's fence.