A fire that enveloped 40 decommissioned SEPTA buses, disrupting Thursday morning’s commute, is believed to have started with a bus battery in a Proterra electric bus, according to SEPTA. A fire department spokesperson confirmed the Fire Marshal’s Office determined a battery to be the cause of the fire,

After a huge fire broke out at SEPTA’s largest bus depot in Nicetown on Thursday, officials have determined a cause for the fire.

The fire broke out at Southeastern Pennsylvania Transportation Authority's facility in Philadelphia's Nicetown-Tioga neighborhood. Up to 40 buses caught fire.