DETROIT (AP) — Tesla is allowing some drivers to use its Autopilot driver-assist system for extended periods without making them put their hands on the steering wheel, a development that has drawn concern from U.S. safety regulators.

The National Highway Traffic Safety Administration has ordered Tesla to tell the agency how many vehicles have received a software update making that possible and it's seeking more information on what the electric vehicle maker's plans are for wider distribution.

"NHTSA is concerned that this feature was introduced to consumer vehicles, and now that the existence...