Montana authorities said an improvised explosive device blew up on an elementary school playground in Helena.
Lewis and Clark County Sheriff Leo Dutton told the Associated Press that nobody was injured when the explosive detonated at the Rossiter Elementary School playground Tuesday morning.
Dutton said no threat was made against the school before the explosion and authorities were investigating. It was not immediately clear if the explosion damaged any property.
Students were being evacuated from the school after authorities made sure the path was clear of other devices.
All schools in Helena and East Helena are locked down and being searched by officers.
The FBI, the Bureau of Alcohol, Tobacco, Firearms and Explosives, and the Montana Highway Patrol are assisting sheriff’s staff and Helena police officials in the investigation.