The Pentagon Force Protection Agency said a lockdown of the facility had been lifted in wake of a shooting at a nearby bus stop.
Hours earlier, a news source confirmed the Pentagon was on lockdown after multiple gunshots were fired near the building.
Employees were notified of the situation.
“The Pentagon currently is on lockdown due to an incident at the Pentagon Transit Center,” the Pentagon Force Protection Agency said in a statement. “We are asking the public to please avoid the area..."
Terace Garnier, a reporter for Newsys, posted footage from the scene of the attack, writing: "Right know the bomb squats is here. There [are] at least 10 fire trucks, 4 emergency trucks, and [more than 10] police vehicles."
Garnier later said "there [was] an ambulance leaving the area" and reported seeing an "armed individual (military with what appears to be an M16) running over to a group of others (in the metro entrance area) that also appeared to be [soldiers]."
She also reported "bomb sniffing dogs [were] checking around the [scene of the incident]," adding that "ATF agents have arrived."
While local police have not announced whether anyone was injured in the event, the Pentagon's Task & Purpose website quoted Politico reporter Lara Seligman as saying the attacker had been shot outside the building and a police officer was injured at the crime scene.