Groton — Town police said the main gate at the Naval Submarine Base has reopened, easing congestion on Route 12 in both directions.

The main gate was closed Thursday night after shots were fired at a man who allegedly brandished a knife at the pedestrian entrance to the main gate of the base. The gate was closed for more than 12 hours as officers investigated the incident.

Two civilian officers were treated and released from Lawrence + Memorial Hospital for injuries they sustained during the incident.