MCMINN COUNTY, TN. (WRCB) -- Two adults, two children, and an unborn child died Friday afternoon in a head-on collision in on a rural road in McMinn County. All victims were immediate family members. It is believed that the mother was driving, the father was in the front passenger seat, and the children approximate ages 2 and 3 years old, were in the backseat.

The accident happened just after 1:00 p.m. when a Dodge Neon and a tractor trailer crashed into each other on Highway 68 near County Road 292. It blocked the highway for more than five hours.

Officials are not sure which vehicle crossed the center line but an eyewitness reportedly saw the pregnant woman driving. The car was traveling eastbound and the truck was going westbound.

Investigators on scene told Channel 3 Eyewitness News the truck began leaking diesel causing a fire. The fire destroyed the cab but did not burn the car. Everyone inside the car was dead upon impact.

Lt. Daniel Ruskey told our partners at the Times Free Press, "This is probably one of the worst [crashes] I've been involved with in 15 years with the Highway Patrol."

Investigators are still trying to piece together exactly what caused the accident. Even though the truck caught fire the driver escaped without serious injury.

The family of four were from the East Tennessee area but no identities have been released.