U.S. safety regulators are investigating Chrysler Group's 2012 recall of 744,822 sport utility vehicles in the United States after six consumers complained of inadvertent airbag deployments even after fixes were made.

The National Highway Traffic Safety Administration said in documents filed on Monday that it had opened a query into the recall of Jeep Liberty SUVs from model years 2002 and 2003, and Jeep Grand Cherokee SUVs from model years 2002 through 2004. The safety agency will study the effectiveness of the previous recall.

Chrysler, a unit of Fiat Chrysler Automobiles, said in a statement that it had notified NHTSA of the six incidents involving inadvertent airbag deployments while the vehicles were in operation and was cooperating with the safety agency's investigation.

Chrysler recalled the vehicles on Nov. 7, 2012, because airbag circuits could degrade.

The company addressed the problem by installing an in-line jumper harness with an integrated electrical filter to eliminate electrical spikes that the company believed were causing the problem, according to the NHTSA documents.

The safety agency had previously opened an investigation of the issue in October 2011 and three months later upgraded the probe.

In the latest six cases in the NHTSA documents, no crashes were reported, but injuries consisting of cuts and burns were alleged.

At the time of the recall in 2012, another 174,723 SUVs were affected in Canada, Mexico and outside of North America. The probe found 215 cases of inadvertent airbag deployments that resulted in 81 minor injuries in the United States but no crashes.