US probes whether recall of Tesla Autopilot driving system did enough to make sure drivers attention

The U.S. government's auto safety agency is investigating whether last year's recall of Tesla's Autopilot driving system did enough to make sure drivers pay attention to the road.

The National Highway Traffic Safety Administration says in documents posted on its website Friday that it has concerns about the December recall of more than 2 million vehicles.

The agency pushed the company to do the recall after a two-year investigation into Autopilot's driver monitoring system, which measures torque on the steering wheel from a driver's hands.

The fix involves an online software update to increase warnings to drivers. But the agency said in documents that it has found evidence of crashes after the fix, and that Tesla added updates that weren't part of the recall.