A burning body was found underneath a Schuylkill Expressway overpass in South Philadelphia early Thursday, officials said.

Firefighters made the discovery about 2:30 a.m. Fire Capt. William Dixon said after firefighters extinguished the blaze in four minutes, they found a "victim severely burned in the debris."

The person, who was pronounced dead at the scene, was discovered on a mattress underneath the eastbound I-76 overpass near Passyunk and Oregon Avenues.

It was not yet known if the victim was male or female.

"We don't know if this body was intentionally set on fire or if it was possibly a homeless person who accidentally caught fire trying to keep warm," Police Chief Inspector Scott Small told reporters at the scene.

An investigation, also involving the city's Medical Examiner's Office, is ongoing.