UPDATE 1-U.S. auto regulator probes Tesla 'Autopilot' crash -source

(Adds details of probe, background, byline)

WASHINGTON, Jan 24 (Reuters) - The U.S. National Highway Traffic Safety Administration (NHTSA) is sending investigators to examine the crash of a Tesla Inc vehicle, apparently traveling in semi-autonomous mode, and a fire truck in California, a person briefed on the matter said on Wednesday.

The move follows an announcement on Tuesday by the National Transportation Safety Board (NTSB) that it was sending two investigators to the scene to conduct a "field investigation" to examine both driver and vehicle factors in Monday's accident in which the driver said the vehicle was operating in "Autopilot" mode.

Tesla declined to comment on the new probe.

The government probes escalates the risk for Tesla and automakers at a time when the industry is seeking federal legislation that would ease deployment of self driving cars.

The NTSB can make safety recommendations but only the NHTSA can order automakers to recall unsafe vehicles or fine automakers if they fail to remedy safety defects in a timely fashion. Before the agency could demand a recall from Tesla, it must first open a formal investigation, a step it has not yet taken.

The NTSB probe is the safety board's second into a Tesla crash that may be linked to Autopilot, the automaker's semi-autonomous driver assist system that handles some tasks and allows drivers under certain conditions to take their hands off the wheel for extended periods.

Tesla requires users to agree to keep their hands on the wheel "at all times" before they can use Autopilot.

The Culver City, California fire department said in a Twitter post that on Monday that an engine was struck by a Tesla "traveling at 65 mph. The driver reports the vehicle was on Autopilot. Amazingly there were no injuries." (Reporting by David Shepardson; Editing by Richard Chang)