Back in 2003 and 2004, General Motors Co made changes to redesigned ignition switch parts on four models but did not ensure that older, and possibly faulty parts were taken out of circulation, the automaker confirmed in a filing with U.S. safety regulators.

This means an unknown number of possibly flawed parts could have been used to repair GM models brought in at dealerships or repair shops after the redesign was made.

No crashes, injuries or deaths have been reported in any of the four older model Chevrolet Malibu, Pontiac Grand Prix and Grand Am, and Oldsmobile Alero that are involved in the issue, according to a GM spokesman.

GM has recalled nearly 29 million vehicles, including about 14.7 million for ignition switch problems. 

Mary Barra, has testified in Washington four times this year, saying that GM is looking into a new culture on consumer safety.

She last appeared in Washington on July 17.

GM informed regulators earlier this year that one of its engineers, Ray DeGiorgio, approved a redesigned ignition switch for small vehicles, including the Chevrolet Cobalt

He did not change the part number however, according to Reuters.

At least 13 people were killed in Cobalt and other small car vehicles with faulty ignition switches, which could cause engines to shut off while driving, leading to a sudden loss of power steering and power brakes and the failure of air bags to deploy in the event of a crash.

DeGiorgio also approved the redesigned ignition switches in the Grand Prix and other models, according to Reuters. No deaths have been linked to that issue.

DeGiorgio was one of the 15 GM employees fired by the company since this year's safety crisis started.

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