Well, that didn’t take long. Just a couple hours after Uber’s fleet of self-driving cars began to pick up passengers in San Francisco for the first time, one of the vehicles was caught running a red light.

The footage, posted on YouTube by a user named Charles Rotter and first reported by the San Francisco Examiner (and later by SFIst), appears to show one of the self-driving Volvo XC90 SUVs used by Uber blowing through a red light, right before a pedestrian crosses the street. According to the Examiner, the footage was from a dashboard camera used by Luxor Cab, a taxi company in San Francisco.

A few hours later, another incident was reported on Twitter.

Just passed a 'self-driving' Uber that lurched into the intersection on Van Ness, on a red, nearly hitting my Lyft. — Annie Gaus (@AnnieGaus) December 14, 2016

(Not enough time to get a good shot, but...whoops!) pic.twitter.com/XK49nMF2Q4 — Annie Gaus (@AnnieGaus) December 14, 2016

A spokesperson said both incidents were under review. “Safety is our top priority,” the spokesperson said. “This incident has been reported and we are looking into what happened.” The spokesperson wouldn’t say whether the car that ran the red light was being driven by the car’s computer or by one of Uber’s human safety drivers.

Safety, of course, is the underpinning of Uber’s push into self-driving technology. Ron Lior, senior engineer for Uber’s self-driving car project, told me last week that the company was motivated to deploy its self-driving cars on public streets in the interest of reducing the number of traffic accidents and fatalities that are caused by human error.

Uber was rebuked by the California DMV for failing to obtain a permit for autonomous vehicle testing. The company argued that because its cars require a human driver at all times, they aren’t covered under the state’s permitting guidelines.

There have been a couple of fender benders, and an instance of one vehicle driving the wrong way on a one-way street, involving self-driving Ubers in Pittsburgh, where the company first rolled out the new autonomous service. No injuries have been reported involving any of Uber’s self-driving cars, either in Pittsburgh or San Francisco.

Update, December 14th, 6:52PM ET: Uber appears to have completed its review, and concluded that it was the human drivers, not the computers, that were at fault.

“These incidents were due to human error,” a spokesperson said. “This is why we believe so much in making the roads safer by building self-driving Ubers. These vehicles were not part of the pilot and were not carrying customers. The drivers involved have been suspended while we continue to investigate.”