The bus left McKinley School on Monday morning and the kids on board were headed out fora day of fun at Bounce U, in a trip organized by the Norris Square Civic Association.
The bus was on the way back on Monday afternoon, and had just passed under Route 213, when the two left rear wheels came off, sending the bus across all lanes.
The bus is operated by Dependability Company in Frankford.
When asked if the tires had been serviced recently, owner Gwen Simpkins said "We are looking through all our records right now." She went on to say she is waiting to hear from State Police investigators to get a better understanding of what happened.
Simpkins said her buses are serviced and inspected regularly, although she does not have a certified mechanic.
"When we need tires and things, we take them to the tire place that gives us our tires and services them," Simpkins said. She declined to give out the name of that facility.
Federal inspectors do spot checks on companies like Dependability. They give the company a score of 51% for maintenance. That means their safety score is right in the middle of the pack, just below the level that would raise alarms.
Simpkins says she's had trouble with vandals recently. Before it went on the road they discovered the bus involved in yesterday's crash had been tampered with, and Simpkins said someone had removed the bolts from the hinges on the hood.
The sponsors of Monday's trip say they've used Dependability before with no problems. They're just glad the accident wasn't much worse.
"The kids are all okay. We had once child who required some stitches and two others were observed for possible concussions and there was none. All the others were checked and cleared," said Maritza Gonzalez of the Norris Square Civic Association.
Pennsylvania State Police say it will take some time before they know exactly what caused the crash.