Police searched San Francisco General Hospital Thursday afternoon and found remnants of an M80 explosive but no evidence of a shooter, after a call near 2 p.m. of an explosion and possible shots fired in the building.

Mission Police Station Captain Daniel Perea told media around 4 p.m. that nobody had been injured in the incident, but that the firecracker appeared to have been set off in a fifth floor hallway.

Police responded to the call shortly after 2 p.m. with dozens of police cars, the bomb squad, and tactical units. They secured the hospital building on the north side of 22nd Street and evacuated the building.

“The building was secured and additional officers conducted a search. During the search we found the remnants of what looked like an expended M80 firecracker,” Perea said.

Though no suspects have been identified, Perea said police will review video footage for possible leads. The San Francisco Sheriff’s Department, UCSF police, and the FBI responded to the scene, though Perea said the FBI’s assistance was ultimately not needed.

Brent Andrew, a spokesperson for the hospital, said no inpatient operations at the hospital were affected by the situation, and ambulances were able to access the emergency room through an alternate entrance despite the shutdown of 22nd Street.

Hospital staff and a patient told Mission Local they knew little about what was happening as the situation unfolded but had heard about the explosion.

“We heard someone say that they heard an explosion, and after that we were told to evacuate,” said Abel Maldonado, a health worker at the urgent care center.

Patient Harry Lloyd was on fifth floor of the hospital when he heard a loud explosion.

“There was a big boom coming from the elevator,” he said. “[Nurses] told us to go to the waiting room and then they told them to evacuate.”

Amanda Dowden, a nurse at the hospital, had been evacuated and watched the situation unfold from 22nd Street and Potrero Avenue. Sherriff’s deputies instructed her to evacuate just before she was slated to finish her shift at 2 p.m. 

“They came and told us we needed to evacuate. They didn’t tell us anything,” Dowden said. She works in an outpatient unit, and said everyone in her building, estimated to be 200 or so, was evacuated.

Other witnesses said that while the hospital is generally loud, with ambulances and police often speeding down Potrero Avenue, the number of sirens on Thursday was of a different order. Daria Siciliano, who lives across the street, said she saw cops in riot gear carrying rifles coming out of the squad cars and rushing to the hospital.

“I always think they overreact, but when I saw the riot gear and rifles I [knew it was serious],” she said. Bomb-sniffing dogs were also in the area, investigating hospital fences and buildings across the street.

Potrero Avenue was closed to traffic from 21st to 23rd streets until about 4:30 p.m.

Bomb squad on Potrero Avenue outside San Francisco General Hospital for the firecracker incident on July 7, 2016. Photo by Joe Rivano Barros.

Bomb squad on Potrero Avenue outside San Francisco General Hospital for the firecracker incident on July 7, 2016. Photo by Joe Rivano Barros.

Squad cars assembled on 22nd Street and Potrero Avenue as officers conduct a search of the San Francisco General Hospital building where a firecracker was set off on July 7, 2016. Photo by Joe Rivano Barros.

Squad cars assembled on 22nd Street and Potrero Avenue as officers conduct a search of the San Francisco General Hospital building where a firecracker was set off on July 7, 2016. Photo by Joe Rivano Barros.