California regulators on Tuesday ordered Cruise, a General Motors subsidiary, to stop its driverless taxi service in San Francisco after a series of traffic mishaps, including one this month when a Cruise car dragged a pedestrian 20 feet after a crash.

The decision by the state’s Department of Motor Vehicles followed a turbulent three months for Cruise. In early August, over the objections of San Francisco officials, state regulators allowed Cruise to expand its service in the city. But a little more than a week later, the D.M.V. told Cruise to cut its fleet in the city in half.

On Oct. 2, a pedestrian was hit by a car, then was hit a by a Cruise vehicle and trapped under the driverless car. As it tried to pull over, the Cruise car dragged the pedestrian until it stopped. Cruise said its autonomous vehicle had “braked aggressively” and blamed the human driver for the incident.

In an initial meeting with Cruise after the October crash, the D.M.V. said, the company showed footage from the car’s cameras that ended with the driverless vehicle coming to a complete stop after hitting the pedestrian. D.M.V. officials later learned through “discussion with another government agency” that the pedestrian had also been dragged, according to a suspension order sent to Cruise.

In a statement, Cruise said it had shown the agency “the complete video multiple times.”

The suspension is a major setback for Cruise, which started testing its autonomous cars in San Francisco several years ago and introduced a limited driverless taxi service in the city last year.

It is also an unwelcome development for the nascent driverless car industry. Big tech and auto companies have invested billions of dollars in the technology, and the expensive cars have in recent months just started to gain some mainstream acceptance. The California regulators’ decision could increase calls for federal regulators to take a closer look at the technology.

“When there is an unreasonable risk to public safety, the D.M.V. can immediately suspend or revoke permits,” the agency said in a statement. It did not say how long the suspension would last.

In a post on X, formerly known as Twitter, Cruise said it would pause its driverless operations in San Francisco and was working on enhancements to the cars’ technology. Cruise can still test its autonomous cars in California, but they must have safety drivers who can take over in an emergency.

On a call with financial analysts on Tuesday morning before the state action, Mary T. Barra, G.M.’s chief executive, said the driverless cars had been involved in far fewer collisions than human drivers, but she acknowledged regulatory concerns.

“We do believe that Cruise has tremendous opportunity to grow and expand,” Ms. Barra said. “Safety will be our gating factor as we do that.” She added an assurance that G.M. had plans to support Cruise’s expansion.

Ms. Barra also said G.M. would have more to say about Cruise when it reported its fourth-quarter earnings in three months and at a daylong investor presentation expected to take place in the first half of 2024. Cruise’s expenses were $700 million in the most recent quarter, according to a transcript of the call.

The Cruise cars have drawn considerable criticism from local safety officials, who complained that they were becoming a nuisance, getting in the way of firefighting and other emergency situations. Those complaints have grown louder in recent months as the Cruise vehicles have been involved in several high-profile incidents.

Shortly after another state regulator, the California Public Utilities Commission, allowed the service to expand, at least 10 Cruise vehicles stopped functioning in the middle of a busy street in San Francisco’s North Beach neighborhood, blocking traffic for 15 minutes. A few days later, a Cruise vehicle drove into a city paving project and got stuck in wet concrete.

The day before the D.M.V. announced its investigation of Cruise’s safety record, a fire truck responding to an emergency call collided with a Cruise driverless taxi on Aug. 17, injuring a passenger in the car.

Less than two weeks ago, Cruise said it had released major updates to the software that operates its driverless cars to help them interact with firefighters and other safety officials. Those updates included the ability to manually take over the vehicle. Emergency responders have had to contact Cruise staff to control the cars remotely when they have gotten in way.

On Oct. 16, the National Highway Traffic Safety Administration opened an investigation into Cruise’s interactions with pedestrians, including the person who was dragged by a Cruise car. In a statement on X, Cruise called the incident an “extremely rare event.”

At a San Francisco County Transportation Authority hearing on Tuesday morning, Aaron Peskin, president of the city’s Board of Supervisors, said the driverless car industry was “not safe and was immune from any governmental regulatory oversight.”

“If there is any vindication of San Francisco’s position, we just got it, whole hog, from the Department of Motor Vehicles today, albeit sadly rather late,” Mr. Peskin said.

As of Tuesday, Cruise had 50 driverless cars running during the day and 150 at night.

Cruise’s main rival, Waymo, will continue to operate its autonomous cars in San Francisco. Waymo, which is owned by Google’s parent company, Alphabet, has avoided high-profile incidents so far. A Waymo spokesperson declined to comment.

Matt Wansley, a professor at the Cardozo School of Law in New York who specializes in emerging automotive technologies, called on the National Highway Traffic Safety Administration to determine whether Cruise’s service should also be suspended in other states where it is testing the same technology.

“If Cruise’s vehicles are unsafe in California, they should be unsafe in other states as well,” he said in an interview with The New York Times. “There are inconsistent regulations across the country.”

Mr. Wansley said that while regulators and experts could readily point to accidents involving Cruise vehicles that would not have happened if a person had been behind the wheel, that was not the case with Waymo’s cars.

“Companies should be judged by their on-road safety performance, and there is a significant difference between Cruise and Waymo,” he said.

Neal E. Boudette contributed reporting from Michigan.