NBC NATIONAL NEWS — Federal regulators have stepped up their investigation into Jeep Liberty airbags.

50 people have now reported they were hurt when the airbags inflated by surprise, without a crash.

The National Highway Safety Traffic Safety Administration has been investigating 2002 and 2003 model years of the vehicle since September.

Safety regulators say the airbag computer may fail due to an electrical voltage spike.

Nearly 387,000 vehicles are under investigation.