A "significant" propane tank leak on a food truck created a vapor cloud that was ignited by cooking grills, causing a fiery explosion that critically injured five people, police said Wednesday.
A transit police officer who rushed to the scene immediately following the explosion late Tuesday afternoon found multiple victims lying in the street, including at least one who was on fire, police said in a statement.
Thirteen people were taken to the hospital by police and firefighters. Five remained in critical condition Wednesday - the truck's owner, her daughter, two other relatives and a 23-year-old man.
Officials say the La Parrillada Chapina truck was licensed to operate in the Feltonville neighborhood of north Philadelphia and was open for business at the time of the explosion.
The 25-foot truck carried two 100-pound propane tanks to fuel its grills. Both tanks were full and one was in use at the time of the explosion. Investigators believe the leak occurred in the other tank, which was later found 95 feet from the truck, police said.
"A propane vapor cloud ... enveloped the truck finding an ignition source at the grills inside the truck causing an explosion and fireball to envelop the entire street," the statement says.
Surveillance video from two businesses captured the explosion, followed by a huge fireball that engulfed the truck and set a utility pole on fire. Two cars driving by the explosion also were briefly engulfed.
The U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives, Philadelphia police detectives and the city fire marshal's office were continuing to investigate whether foul play was involved, police said.