Manufacturing problems with Takata Corp. air bags go beyond what the Tokyo-based company has disclosed to U.S. safety regulators about why the devices are at risk of exploding with dangerous force, according to internal company documents reviewed by Reuters.

Takata has cooperated with a probe begun in June by U.S. National Highway Traffic Safety Administration investigators into whether its air bags contain a defect in the inflator — the device at the core of the air bag that allows it to inflate in a fraction of a second in the event of a crash.

Specifically, the NHTSA has been looking in part at whether some Takata air bag inflators made between 2000 and 2007 were improperly sealed, a flaw that could expose the explosive inside and cause the air bag to blow apart in an accident.