Federal safety regulators are upgrading their investigation of consumer complaints of engine fires in the 2007 Chrysler Pacifica SUV. Ssafety regulators at the National Highway Traffic Safety Administration (NHTSA) reported the fires may be related to a faulty power steering seal.

There are 51,590 of the Pacific SUVs with the 4.0 liter engine that might be at risk of erupting into flames under the hood.

The reports of smoke and fire are contained in 3 complaints to NHTSA and 25 complaints to the automaker, according to documents posted on the NHTSA web site.

Chrysler has also received 166 warranty claims related to the fire problem.

Complaints alleged that a fire erupted under the hood, near the front of the vehicle, according to the Office of Defects Investigation (ODI) at NHTSA.

Chrsyler, according to NHTSA, asserts that the alleged defect occurs only in the in the 4.0 liter engine and the consumer will experience a loss of power steering fluid or a noisy power steering pump before seeing any evidence of smoke or fire.

Chrysler also states, according to NHTSA, that a tube nut on the high pressure power steering line was discovered to be cross threaded during the assembly process and did not allow proper sealing of the o-ring.

Chrysler assembles the 4.0 liter engine used in the 2007 Pacifica. The 3.8 liter engine also used in the vehicle arrives at the Chrysler plant already assembled and apparently does not present a fire hazard.

Chrysler, according to NHTSA found it was possible to cross thread the tube nut on the high pressure line during attachment to the steering gear, thus creating an improper seal.

NHTSA reported on its web site that Chryslers has implemented assembly process changes to eliminate the possibility of cross threading and applied additional quality control measures to detect power steering fluid leaks.

Chrysler told federal safety regulators that the changes have minimized the cross threading problem but ODI reports that a review of the warranty claims indicates that the alleged defect has not declined.

ODI is began a engineering analysis February 21 of the fire hazard. The investigation could eventually lead to a recall of the 2007 Chrysler Pacifica.