A dump truck towing a skid steer was traveling eastbound on I-78 in Upper Macungie Township near Route 100 just before 10 a.m. when the cargo struck an overpass, splitting the cab from the truck bed, state police said.
The truck rolled until coming to rest near the mile 48 marker, they added.
The Lehigh County Coroner's Office confirmed that the dump truck driver and a passenger were killed in the crash, but did not identify the victims pending notification of family members.
The entire highway between Routes 863 and 100 was closed Monday morning while emergency workers cleared the way and investigated the scene, authorities said.
Westbound lanes of I-78 reopened at 2:30 p.m., while eastbound lanes are still shut down as of Monday evening.
Click here to follow Daily Voice Lower Merion-Narberth and receive free news updates.