Federal traffic safety regulators are looking into suspected problems with Elon Musk's test run of self-driving "robotaxis" in Texas after videos surfaced showing them braking suddenly or going straight through an intersection from a turning lane and driving down the wrong side of the road.

The National Highway Traffic Safety Administration said Tuesday that it has asked Tesla for information about the apparent errors. Though many other videos show robotaxis driving perfectly, if regulators find any major issues, that would likely raise questions about Musk's repeated statements that the robotaxis are safe and his claim that Tesla will dominate a future in which nearly all cars on road will have no one behind the wheel ' or even need a steering wheel at all.

"NHTSA is aware of the referenced incidents and is in contact with the manufacturer to gather additional information," the agency said in a statement. Passengers in Tesla robotaxis on the road in Austin, Texas, have generally been impressed, and the stock rose 8 per cent Monday. Investors grew more cautious Tuesday after news of NHTSA's inquiry, and the stock fell more than 2 per cent.