U.S. federal agents say two small devices found at a bookstore in Colorado partially detonated, causing minor damage but no injuries.

Bomb squad officers and other authorities were dispatched after the devices were spotted Saturday at the bookstore in a mall in the Lakewood area. The discovery was made after police responded to a report of a break-in.

The FBI says the two “small, crude devices” caused minimal damage in a small area in the bookstore, but no damage to the mall.

FBI agents are investigating the case.