Four persons died in a fiery collision yesterday when their car was hit by a dump truck, which then pushed it into a second truck that was loaded with bricks, Fairfax County police reported.

Police said the four who died in the accident near Chantilly at the intersection of Rte. 50 and Sully Road could not immediately be identified because their bodies were so badly burned. They said the bodies appeared to be those of two men and two women, one of whom may have been pregnant.

The car, a 1966 Dodge, bore license plates from Ashburn, Va., police said.

According to police spokeswoman Betty Bosarge, the dump truck was headed east on Rte. 50 and went through the light at Sully Road (Rte. 28) about 2:30 p.m.

She said the truck collided with the car, which had a green light and was making a right turn from Sully Road on to Rte. 50.

The car was pushed across the intersection, over a median strip and into the truck loaed with bricks, which was waiting to turn left from Rte. 50 on to Sully Road, Bosarge said.

The gas tanks of the car and the dump truck exploded at that point, Bosarge said, and shortly thereafter fuel spilled in the crash ignited the brick truck.

Although the drivers of both trucks escaped uninjured, the four occupants of the car were trapped in their vehicle, which was crushed between the trucks.

It took firemen about 15 minutes to put out the fire, according to fire department spokesman Lt. L. D. Jackson.

"They didn't know there was a car with bodies in it until they knocked the fire down," Jackson said.

It took nearly an hour and a half to clear the wreckage sufficiently to remove the bodies. One body was protruding from the car's rear window and the other three appeared stacked on top of each other.

A charred purse and auto license tag found in the wreckage were expected to help in the task of identifying the dead.

The bodies were taken to the Fairfax County medical examiners office Police said three were burned so badly that identification through fingerprints would be impossible. They said x-rays and examination of dental records would be used in the identification efforts.

Traffic was rerouted around the accident scene in western Fairfax County for several hours. Many of the firemen and policemen on duty there had to be relieved periodically because of the intense heat.

The police investigation of the accident was continuing last night.

The traffic light at the intersection where the accident occured has been the object of complaints from some motorists recently.

They complain that the four-way bank fo lights at the intersection sometimes malfunctions, switching suddenly from green to red without a warning yellow, at other times turning green in all directions. They say such malfunctions have been responsible for several previous accidents at the intersection, including one fatality.

The complaints have never been officially verified. Both police and state highway officals say that whenever they have investigated, the lights have worked properly.