The US Congress will begin hearings into why General Motors failed to correct defects in ignition parts.

The hearing will start on Tuesday, just as GM has had to recall another 1.3 million vehicles, bringing the total to more than six million.

The flaw, known to GM engineers and their suppliers for more than 10 years, is an ignition key switch. Heavy key chains, or a knock to the switch, can disable steering, braking and passenger airbags while the car is in motion.

The total projected cost to the company is more than $1bn.

But GM is legally immune from paying damages for any accident that occurred before its emergence from bankruptcy in 2009.

The Justice Department is investigating whether the company committed bankruptcy fraud by not disclosing the defects before then.

Al Jazeera's Tom Ackerman reports from Washington DC.