Police: San Diego school blast a prank

SAN DIEGO, May 7 (UPI) -- San Diego authorities say a small explosion at a middle school was caused by a 12-year-old who said the blast was a prank.

Police said the Wagenheim Middle School student admitted to constructing a homemade device containing dry ice and placing the item in a school trash can, where it detonated at the start of the day, the Los Angeles Times reported Wednesday. Investigators said the student implicated four other boys.

Authorities said the device caused more noise than damage -- it created a loud boom, but the trash can contained the blast and remained intact after the detonation.

School spokesman Jack Brandais said students were sent to the playground while bomb safety experts ensured the school was safe.

"This is purely precautionary," he said.