Reports of airbag burn injuries and airbag components setting fire to other parts of the vehicle interior have prompted US safety regulators to intensify another investigation into defects in Ford's Focus compact car, according to a Reuters report.

The report said there have been 130 complaints of burn injuries from Focus airbags as well as 18 reports that the deployed airbags caused other parts of the vehicle to catch fire.

The car – a strong seller on both sides of the Atlantic, and about to be launched in Australia and New Zealand, was introduced in the US in 2000, intended to lure young buyers to the Blue Oval, but has so far been subject to nine safety recalls while six investigations into possible defects are still pending, Reuters said.

The news agency said the National Highway Traffic Safety Administration (NHTSA) earlier this month upgraded the investigation into 576,700 of the 2000 and 2001 model year Focus cars to an engineering analysis, a step that often precedes a recall, adding that NHTSA reported that Ford had received 100 complaints about the Focus' airbags, adding to the 40 already made to NHTSA.

The Reuters report and others circulating in the US say there are real signs that regular negative publicity over recalls or alleged safety defects is hurting Focus sales – it is now outsold by GM’s ageing Chevrolet Cavalier, for example – and the car has been given an advertising push by Ford chairman Bill Ford himself.

Ford claims to have improved Focus quality and warranty claims are down, the latest Reuters report also said.