US officials are combatting counterfeit airbags, one of which shot flames and shards of metal shrapnel at a crash dummy during a simulation.

In government tests of 11 counterfeit bags, ten did not inflate or failed to inflate properly.

"These airbags don't work. They aren't going to save you in an accident," said Immigration and Customs Enforcement director John Morton.

"They are a fraud and a danger from start to finish and you don't want them in your car," he added.

Around 2,500 counterfeit airbags have been seized by law enforcement authorities so far this year, Morton told reporters.

The counterfeits typically look like authentic airbags and often include a manufacturer's logo.