EPHRATA - The Grant County Sheriff's office has lost an M4 rifle, and the Washington State Patrol is investigating. The weapon had not been recovered as of Friday.

"I am enormously concerned about this missing rifle," Sheriff Tom Jones said. "I am sorry to alarm the public that such a weapon has been lost from our control, and I reassure everyone that we will find the rifle, and anybody who is found to be responsible for any malfeasance will be held accountable at the highest level."

The rifle was unaccounted for during a recent GCSO internal routine audit and equipment inventory. It was last logged into a secured firearms room at the Grant County Courthouse in Ephrata.

Immediately after the M4 was discovered missing, the GCSO conducted an internal audit and investigation to try and locate the rifle, Jones said. When the rifle was not found, Jones asked the Washington State Patrol to investigate.

The M4 rifle is made by Colt Firearms. It is similar to the M16 rifle used by the U.S. military, but the M4 has a collapsible butt stock and shorter barrel. It fires a 7.62mm round.

The GCSO uses the M4 as a rifle issued to patrol deputies and the weapon is commonly used by law enforcement agencies nationwide.