Vogt, 38, offered little in the way of explanation, stating simply "I have resigned from my position," according to his email to staff viewed by Reuters on Sunday.

"The last 10 years have been amazing, and I'm grateful to everyone who helped Cruise along the way," he wrote in the email.

Cruise this month pulled all of its vehicles from testing in the U.S. to conduct a safety review after an Oct. 2 accident that involved another vehicle and ended up with one of Cruise's self-driving taxis dragging a pedestrian.