By Greg Bensinger

SAN FRANCISCO (Reuters) -General Motors’ autonomous vehicle unit, Cruise, is facing multiple federal investigations over its cars’ safety, including two incidents where the robot cars appeared not to yield to pedestrians in crosswalks, according to a U.S. regulator's letter released on Friday.

Cruise autonomous cars "may not be exercising appropriate caution around pedestrians in the roadway," according to the letter dated Oct. 20 from the National Highway Traffic Safety Administration. "This vehicle behavior could increase the risk of a collision with a pedestrian which in turn may result in injury or death."

NHTSA previously made public another Oct. 20 letter in which it raised concerns over several hard-braking incidents by Cruise vehicles that resulted in collisions.

Safety officials cited two videos where Cruise vehicles came close to pedestrians in crosswalks and appeared to nearly strike them. In one, the vehicle is observed steering toward a pedestrian walking a dog, before braking, causing the pedestrian to pause and pull back on the leash. In the other, the car appears to narrowly avoid striking four pedestrians in a crosswalk, including two small children, before it continues down the street.

Asked about the videos, Cruise said on Friday the vehicles were tracking all pedestrians in both cases and that it has "made improvements as part of our process of continuously enhancing our technology to give pedestrians more space around our vehicles."

The company said of NHTSA's inquiries that it "cooperated with each of their requests to date as part of the ongoing investigation process and will continue doing so."

NHTSA said it was seeking additional information from Cruise about the pedestrian incidents including all videos running from at least 30 seconds before and after each event and composite renderings. The agency is seeking the information by the end of Oct. 27.

The NHTSA probes add to Cruise’s October woes after the California Department of Motor Vehicles ordered the driverless cars to be removed from state roads, calling them a public hazard and alleging the company had "misrepresented" the safety of the technology.

Cruise had been operating an Uber-like service with unmanned vehicles, primarily in San Francisco, but the company halted that service this week. It is still allowed in the state to test autonomous cars with human safety drivers.

Cruise is competing with Alphabet’s Waymo unit, and others, to develop the robot cars for wider production and deployment. Perfecting the technology will take years of real- world testing, but the companies have run in to resistance from some lawmakers and citizens who said they fear the vehicles are as yet unproven and pose a safety risk.

Cruise and Waymo have deployed the cars in several states in addition to California, including Arizona and Texas. As of Friday, Waymo vehicles continued driverless passenger operations in San Francisco, its main hub.

The Teamsters union, which has publicly opposed the broad rollout of autonomous vehicles, said Cruise's decision to pause driverless operations nationwide "is a major concession by the industry."

"It’s a cautionary tale of what happens when we let AV companies govern themselves."

(Reporting by Greg Bensinger in San FranciscoAdditional reporting by David Shepardson in WashingtonEditing by Matthew Lewis)