The driver of that Lancer has been identified as Michael Doughan, 29, of Philadelphia. Three other victims, also from Philadelphia, were identified as Patrick Chang, 37, Jason Stefaniuk, 33, and William Eder, 23.
Police know that Doughan, Chang and Stefaniuk were wearing their seatbelts, but investigators have been unable to determine if Eder was wearing his.
Investigators said Monday that speed and alcohol are suspected factors in this crash.
Police say the Lancer was travelling speeding southbound between Allegheny and Girard Avenue, making several lane changes. Upon approaching Girard Avenue, the car was in the left lane and made a sudden steering change into the right lane. That's when, police say, the driver lost control.
The car began a clockwise slide, and the left front of the car slid under the left rear of tractor trailer, which was in the right southbound lane of the highway. The car continued to rotate and one of the men was ejected from the car. The vehicle came to a final stop on the southbound exit ramp of Girard Avenue.
RELATED SLIDESHOW: Pictures from the crash scene
The truck driver, 57-year-old Frank Maier, was not injured.
The accident remains under investigation by state police. Police are asking any witnesses to contact them at 215-560-6199.