Nearly 2 million vehicles are back on U.S. roads after they were involved in an accident where an airbag deployed over the last 2 years, Carfax data shows. Each of those vehicles represents an opportunity for a scammer to install a counterfeit airbag as a replacement. Those counterfeit airbags put owners at risk, according to the National Highway Traffic Safety Administration (NHTSA).

Although instances of that actually happening are believed to be rare, law enforcement officials agree that no one knows for sure how many substandard airbags are in cars today. But the results can be tragic: There have been 3 deaths and 2 severe injuries just in the last nine months because of these airbags, NHTSA reports.

Ten states have more than 40,000 vehicles back on the road after an airbag deployment:

“If consumers own or are considering the purchase of a used vehicle, NHTSA urges them to learn their vehicle’s history and ensure their vehicle has genuine air bag inflators,” the agency said in a release this week. “If their vehicle has one of these inadequate replacement parts, it could kill or critically injure them in a crash.”

NHTSA and federal law enforcement officials say there’s no way to know for sure just how many counterfeit airbags are being installed in U.S. cars today. A new car today can have up to 10-15 airbags installed.