U.S. auto safety regulators have expanded an investigation into malfunctioning air bag controls to include 12.3 million vehicles because the bags may not inflate in a crash.

As many as five deaths are blamed on the problem. The probe covers parts made by made by ZF-TRW that were installed in Toyota, Honda, Kia, Hyundai, Mitsubishi and Fiat Chrysler vehicles from the 2010 through 2019 model years.

Government documents say electrical signals can interfere with a circuit that monitors crash sensors. The interference can damage the circuit.