A battery on a decommissioned electric bus started the fire that burned 40 buses at SEPTA’s Midvale lot on June 5 near the border of Germantown and Nicetown. The cause was announced Friday after an investigation by the Philadelphia Fire Marshal's office. 

According to SEPTA Director of Media Relations Andrew Busch, the bus had been drained of fuel and lubricants and was no longer in service.

Transit police received reports of a fire around 6:17 a.m. that morning. Three minutes later, transit police and the Philadelphia Fire Department arrived on scene. During a press conference, SEPTA Police Chief Charles Lawson highlighted the efficient coordinated response by local, state, and federal agencies, and employees onsite in controlling damages. 

The Midvale lot holds decommissioned and replaced buses slated to be sold or scrapped. It is used by SEPTA employees to pick up vehicles for shifts. During the fire, employees helped to move fences and vehicles to allow hose access. 

At the press conference, SEPTA General Manager Scott Sauer said, “We greatly appreciate the coordination and the effort on the part of our Philadelphia Fire Department. Truly world-class fire department we have. … Everyone at the Office of Emergency Management sprung immediately into action, and we were able to really tamp down the amount of damage that was possible here.”

After the flames were extinguished, a team remained onsite to monitor the air quality on a minute-to-minute basis. Air quality became a concern on Thursday, according to Philadelphia Health Commissioner Dr Palak Raval-Nelson, as heightened levels of benzene, ethyl benzene, and carbon monoxide remained. She advised residents to shut windows and vents. Late on June 6, the recommendation to shut windows and stay out of the area was canceled. 

Out of the 40 buses damaged, 15 were electric vehicles created by manufacturer Proterra, which filed for Chapter 11 bankruptcy in August 2023. The SEPTA fleet of 25 Proterra buses were pulled in January 2020, fewer than six months after SEPTA bought them for $24 million.

On Nov. 9, 2022, a Proterra bus caught fire at a different SEPTA holding lot due to an issue with its coolant. Proterra buses have ignited in multiple locations, including Connecticut and California. In October 2024, citing fire hazards, the Federal Transit Administration issued a recall of 483 Proterra buses.

Although the depot is meant to temporarily hold buses for under a year — about 100 are replaced annually — the electric vehicles were there much longer due to ongoing litigation between SEPTA and Proterra. According to Busch, since litigation started, SEPTA stopped pursuing repairs to get buses back into service and focused instead on reducing costs. During the press conference, Sauer expressed frustration over the lengthy delay and said he had feared a potential fire risk. 

“I’ve already talked to our operations people about moving [electric buses] off site,” Sauer said. “We have to get them off of our property, away from the potential where we could have an incident like this that could have been far worse. We don't want to lose an entire facility, and more importantly, we don't want to hurt anyone.”