DETROIT (AP) — Government safety regulators have expanded an investigation into gas tank fires in oldermodel Jeep Grand Cherokees.

The National Highway Traffic Safety Administration said today that it has added Cherokee and Liberty models to the probe, which began nearly two years ago.

The probe now covers an estimated 5.1 million vehicles and is focused on the SUVs’ gas tanks, which are mounted between the bumper and rear axle. The tanks can be damaged in a rear-impact crash and leak, causing fires. The agency says 15 people have died in 26 Grand Cherokee fires.

The investigation affects 1993 to 2004 Grand Cherokees as well as 1993-2001 Cherokees and 2002-07 Liberty sport utility vehicles. Cherokees, which are no longer made, are smaller than the Grand Cherokee.

An analysis of crash data found that deaths from rearimpact crashes and fires occur more often on the three Jeep models than on comparable vehicles, the agency said.

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