Ford and Mazda have issued a fresh warning to US owners of 475,000 vehicles still fitted with faulty airbag inflators, produced by the now defunct Japanese supplier Takata Corporation, to stop driving them.

The automakers said the warning was targeted at owners of 374,000 Ford, Mercury and Lincoln plus 83,000 Mazda vehicles sold between 2003 and 2015 which are still fitted with Takata airbag inflators similar to those which have been blamed for a string of serious injuries and deaths over the last two decades.

The US National Highway Traffic Safety Administration (NHTSA) said the faulty Takata inflators could explode with too much force in the event of a crash, causing fragments of the metal canister to shoot out, potentially causing severe injuries and deaths.

The US government said 27 people had been killed and 400 injured in the US by the defective Takata inflators which use volatile ammonium nitrate to create a small explosion to inflate the airbags in a crash. Over time, and with prolonged exposure to heat, the chemical can deteriorate and become very volatile.

Ford and Mazda are urging existing owners to stop driving these vehicles and make an appointment to replace the faulty inflators.

A large number of other vehicle brands were also affected by the same recall.