Location of the Shuttle Fire

An M2 bus caught fire on Monday in the Longwood Medical Area, forcing the evacuation of the small number of commuters traveling on the bus.

As the bus was pulling away from Vanderbilt Hall at around 4:30 p.m., a residence building on the corner of Longwood Avenue and Avenue Louis Pasteur, a man came out of Vanderbilt to alert the driver and passengers that a part of the bus was aflame, according to Andrew J. Olive, a passenger on the bus.

Olive, a graduate student in microbiology and immunobiology at Harvard Medical School, said he could smell something burning in the air but did not see anything on fire.

In a statement, Diana C. Pisciotta, a spokesperson for the company that manages the shuttles, said that another bus driver notified the dispatcher and the driver about smoke coming out of the back of the bus.

Six people, including the driver, were on board, she said.

Upon exiting, Olive and the other passengers moved away from the bus, which was still “dropping fire balls” from the back, and walked down Avenue Louis Pasteur towards Boston Latin School, Olive said. Five minutes later, the fire department showed up and blocked off the area.

On Tuesday, an inspector from the Department of Public Utilities found that a malfunction of the alternator caused a belt to burn, Pisciotta said in the statement. That caused the hydraulic fuel tank to rupture, fueling the fire.

“It was a very minor issue,” she said in a phone interview. ‘The bus was taken out of service for repairs, and no one was hurt.”

Boston Fire Department spokesperson Steve MacDonald confirmed that when the fire department showed up, all passengers were safely off the bus. The firefighters extinguished the fire in the back of the bus, and no one was injured.

By that time, a crowd had gathered, with passersby snapping photos and taking videos of the incident, Olive said.

—Staff writer Leanna B. Ehrlich can be reached at lehrlich@college.harvard.edu.