The Central Subway’s Chinatown-Rose Pak Station was evacuated for an hour Sunday after "faulty smoke detectors" set off a fire alarm, San Francisco Fire Department officials said.

Firefighters responded at around 4 p.m. after smoke detectors in two elevator shafts activated fire alarms. The incident happened during the new $2 billion subway’s second day ever in operation.

“After SFFD determined this was caused by a system error, we reset the fire alarm,” SFFD Capt. Jonathan Baxter said. “The fire alarm would not reset due to the faulty smoke detectors.”

The San Francisco Municipal Transportation Agency closed the station to street entry while T-Third Street trains bypassed the station’s platform.

Baxter said transportation agency engineers arrived on scene and that resetting the system required shutting down power to the elevators.

The subway is currently only open to passengers on weekends during a "soft launch period" while feedback is collected from riders and issues are fixed, an agency spokesperson said.

The SFMTA has been contacted for comment relating to the smoke detector incident.

This is a developing story and will be updated.