PHILADELPHIA (WPVI) — A fire that damaged 40 decommissioned SEPTA buses at a Philadelphia storage yard on Thursday was caused by a battery on an electric bus, according to SEPTA.

(The video in the player above is from previous coverage.)

Employees reported the fire around 6:15 a.m. at the SEPTA Midvale District, next to the Roberts Yard, in the 2400 block of Roberts Avenue in the Tioga-Nicetown section of the city.

It was upgraded to a 3-alarm blaze around 7:30 a.m. Thick, black smoke could be seen billowing in the air at the height of the fire.

When the smoke finally cleared, some of the buses could be seen melted to the ground.

A total of 100 buses were in the yard, including gas-powered and electric buses.

Of the 40 decommissioned SEPTA buses, 15 were electric, officials said. They were slated to be sold for a “nominal amount” or scrapped, SEPTA Interim General Manager Scott Sauer said.

Decommissioned buses are generally stored in the area for a year or less while SEPTA makes arrangements to dispose of them.

The electric buses involved were made by Proterra and had not run in several years. Sauer said SEPTA is involved in ongoing litigation with Proterra, and the buses were still being stored as part of the litigation.

When they were put into storage, Sauer said the batteries were disconnected, the coolant was drained and the buses continued to be inspected in accordance with manufacturer recommendations.

In 2022, a coolant issue was to blame for a fire in another Proterra bus located at a different depot.

No injuries were reported in the incident.

Asst. Fire Chief Charles Walker said during a news conference that firefighters encountered several challenges, including access to the fire scene and water supply issues.

Walker said SEPTA workers were able to move buses that were not yet on fire so firefighters were able to get to the flames.

Once they were able to get more water to the scene, crews were able to make progress extinguishing the fire.

Explosions were heard during the fire, which Walker attributed to tires bursting from the extreme heat.

The ATF responded because the K-9 training center is on-site with small amounts of explosives. All explosive devices were quickly removed.

Midvale Depot is SEPTA’s largest facility, which is used for both maintenance and storage. Some 600 employees work there on any given day.

The fire sent a large plume of smoke into the sky, and the Philadelphia Department of Public Health said pollutants were detected in the air.

Officials say the air quality has since returned to normal levels.