Update 5:42 p.m.:  CBS Radio (KYW-1060AM) is reporting that traffic has begun moving again, after reaching a backup length of about 8 miles. 

Early reports from the Turnpike Commission indicate that the truck might have blown a tire, sparking a fire that then spread to some of the cars being transported. This has not been confirmed by investigators at the scene.

Original story continues below

A truck fire halted traffic in both directions of the Pennsyvlania Turnpike in Chester County Thursday afternoon.

A car-carrier truck caught fire around 3:09 p.m. Thursday in the westbound lanes near Route 29, at mile 319 between the Valley Forge and Downingtown interchanges, according to a Turnpike Commission spokesperson.

As of 4:06 p.m., the truck had been moved to the shoulder, but traffic was still stopped in both directions, resulting in a four-mile backlog.

There is no word yet on the cause of the fire.

Sources indicate that Paoli Fire Company responded to the scene. Lionville Fire Company also responded to assist.