Federal regulators said they are expanding an investigation into Waymo this week, following reports that the company's self-driving cars navigated around school buses stopped on the road in Austin, Texas.

In a letter to Waymo dated Dec. 3, the National Highway Traffic Safety Administration (NHTSA) said it will investigate the performance of the autonomous vehicles and their ability to follow traffic safety laws. Reuters first reported the news.

The Austin Independent School District told CBS News it is now aware of 20 incidents this school year in which a Waymo vehicle illegally passed a school bus. All 50 U.S. states have laws requiring vehicles to halt for a stopped school bus with flashing red lights and a deployed stop-arm signal, according to the NHTSA.

Waymo said it id

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