Pentagon entrances were briefly locked down early Tuesday morning in response to a report that gunshots were fired near the building.
Pentagon spokesman Maj. Chris Perrine said a civilian reported possible gunfire by the building's south side about 5 a.m. "Security didn't hear anything, but someone told them there could have been shots fired," he said. Authorities did a sweep of the area but found nothing suspicious. Roads and entrances were reopened a half-hour later.
Security has increased at the Pentagon since the shooting in March, when 36-year-old John Patrick Bedell opened fire at a security checkpoint, injuring two police officers. Three officers returned fire, killing the shooter.
The Associated Press contributed to this report.