SEOUL, South Korea — A commuter bus struck more than 30 vehicles stopped at a traffic light during the morning rush hour Wednesday in Seongnam, just south of Seoul, injuring dozens of people, fire officials in South Korea said.

At least 57 people were being treated for injuries, including nine who were seriously hurt, although none were in life-threatening condition, according to the fire department of Gyeonggi Province, which governs Seongnam.

The bus collided with 32 vehicles before slamming into a median strip, fire officials said. Photos from the scene showed the bus perched on a median strip with a shattered windshield and other damaged cars.

Police were questioning the bus driver, who tested negative in a breathalyzer test and told investigators that the brakes had failed, according to Park Chang-gon, an official from Seongnam’s Bundang district police station.