Investigators say four Asheville, NC, police officers were injured by a blast that went off no more than a foot away from them while they were on patrol Saturday.

The officers had to have metal shrapnel removed from their skin after someone threw an explosive device at them.

It happened about 9:45 p.m. as Housing Unit officers were patrolling a public apartment complex on foot.

Officers said while checking around some buildings they noticed sudden movement, followed almost immediately by a blast near their heads.

They believe it was one person who intentionally attacked them. However, they did not see the suspect. Police say the officers took a defensive stance, called for backup and waited for EMS to arrive and treat the officers who had been hit.

Police believe the explosive was a commercial firework that was combined with shrapnel to create a weapon, WLOS TV reports.

The Asheville Police have requested help from the public in identifying the suspect.