Montana bomb: IED explodes in elementary school playground just before classes begin

Explosion has puzzled investigators, and put authorities on alert in police forces as far as New York

A bomb has exploded at an elementary school in Helena, Montana, just before classes were set to start, according to authorities who are searching for clues as to the reason behind the improvised explosive device in the unlikely American target.

The explosion in the state's capital city followed after no threats were made against Rossiter Elementary school, Lewis and Clark County Sheriff Leo Dutton told the Associated Press. Mr Dutton also indicated no children were harmed.

“There’s a lot of unanswered questions,” Mr Dutton said. “We’re going through it methodically and slowly, so we don’t miss something.”

The device exploded at about 8.21 am. It was not immediately clear if any property was damaged in the incident, either.

A news conference is set for Tuesday morning, and students have been evacuated to give emergency responders the ability to ensure that no further devices were found.

Those children were sent to a separate facility, where authorities were instructing parents to pick them up.

“I didn’t get too close of a look because once they came over, I just barely noticed it when they came over, and then they said that we had to get away from that area, just in case,” third-grader Abigail Lee, who claims she saw remnants near a basketball hoop, said. “There was like a dent in the ground.”

The incident has sparked curiosity beyond Helena, too, with the New York Police Department's counterterrorism unit tweeting shortly after the incident that it was monitoring the situation.

The Associated Press contributed to this report