Coronado police said Thursday afternoon that the main gate to NAS North Island was closed until further notice.
People trying to access the base were told to use the First Street or Ocean Boulevard gates until the main gate at 3rd Street and Alameda Boulevard reopened.
Several members of law enforcement and their vehicles were spotted near the gate at 3:15 p.m.
A short time later, police said the gate had been reopened to traffic.
It's not yet clear what had prompted the closure.