It happened in the westbound lane, said Trooper Nathan Branosky on Twitter. PennDOT traffic cameras showed a cloud of smoke billowing from a large vehicle near Exit 51 on Tuesday morning.
Westbound traffic was being detoured to Exit 53/State Route 309 as firefighters worked the scene, Branosky said. The eastbound lanes remained open with delays expected, he added.
It's not clear what caused the fire, and troopers have not reported any injuries.
Click here to follow Daily Voice Lower Merion-Narberth and receive free news updates.