A major hospital in San Francisco was briefly put under lockdown Wednesday after a loud noise was mistakenly reported as gunfire, police said.

Three buildings at San Francisco General Hospital were evacuated as dozens of law enforcement officers swarmed the area shortly before 1 p.m., said officer Albie Esparza, a San Francisco police spokesman.

Police officers and sheriff’s deputies searched the campus after they received a report from a hospital staffer of a shot fired and a person running away from the hospital, Esparza said. The staff member reported the noise in an outbuilding.

The building is used for offices and research and does not provide any patient care, said Rachael Kagan, a hospital spokeswoman.

Authorities determined there was no evidence of a shooting, and the hospital was given an all-clear and reopened shortly before 2 p.m., Esparza said.

The loud noise may have been caused by construction on the hospital’s campus, Kagan said.

The incident caused a bit of panic at the University of California, San Francisco, which is affiliated with the hospital. The university sent out tweets and emails stating that shots had been fired at the hospital and encouraging those on-site to lock all doors and stay out of sight.

Kagan said the rumors online simply got out of control.

“Nothing was found,” Kagan said. “Everyone is safe.”