Preliminary reports indicate the accident in Jasper County occurred on Thursday night when the Jeep stopped behind a tractor-trailer near a work zone.
A tractor-trailer behind the Jeep failed to stop, rear- ending it and sending it plowing into the semi in front. The Jeep exploded into flames, which also spread to the two trucks.
After firefighters extinguished the flames, they found two bodies in the Jeep.
But the car was so severely burned and mangled, fire crews took it to the Keener Township Fire Department to remove the victims, CNN reported.
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"There were a total of three adults and four children found inside the vehicle," the Indiana State Police said in a statement.
An investigation is under way, but alcohol and narcotics are not believed to be factors, authorities said.
Police identified the dead as Indiana residents Lindsey Williams, 27; Arielle Goldman, 3; Yazmin Goldman, 5; Amado Mangual, 49; and Atlanta residents Jamin Osborne, 5; Jasmin Osborne, 7; and Yvette Williams, 35.
One of the truck drivers was hospitalised while the other one was unhurt.