Police say a stolen U-Haul truck that prompted the evacuation of City Hall in downtown Oklahoma City is empty.

Bomb technicians examined the vehicle that was found unattended near City Hall on Wednesday morning but found nothing inside when the truck's rear door was opened. Workers were allowed to return to their buildings shortly before 10:30 a.m.

Police Capt. Dexter Nelson says nearby buildings had been evacuated as a precaution.

Nelson says Oklahoma has always been a "hyper-vigilant" state after the Oklahoma City bombing, and that Monday's bombings at the Boston Marathon give even more reason for caution.

On April 19, 1995, Timothy McVeigh detonated explosives packed into a yellow Ryder rental truck, killing 168 people in and near the Oklahoma City federal building.