The investigation, prompted by a request from the Center for Auto Safety, will focus on gas tank placement and protection, CNNMoney.com reported Wednesday.
CAS, an industry watchdog group, said 172 crashes with the vehicle have involved fires in which 254 people have died. The model years in question have inadequately protected gas tanks that are especially vulnerable in rear-end crashes, CAS said.
About 3 million Grand Cherokees could be a risk, CAS said.
Chrysler Group spokesman Scott Brown said, "The 1993-2004 Jeep Grand Cherokee meets or exceeds all applicable federal safety (regulations) and has an excellent safety record."
The company said it would cooperate with the investigation.