LONDON — A car crash that injured 11 people Saturday outside London’s popular Natural History Museum was a traffic accident, not a terrorist attack, London police said.

The accident had sparked fears of an attack because it involved a car hitting pedestrians at a crowded site favored by tourists to the British capital.

A massive police presence descended on the museum district minutes after the accident at 2:20 p.m. as police tried to determine if there was a threat to public safety. It took nearly four hours before they decided it was not terror-related.

Police say one man at the scene, thought to be the driver, was detained. He has not been charged or identified.

Witnesses described a panicky rush to leave the scene, nearby shops were evacuated and the sprawling museum, a favorite site for families with children, closed down early. Police established a large security cordon around the area within minutes, closing some roads, and police helicopters hovered overhead.

London Ambulance Service said nine of the 11 injured people were taken to a hospital for treatment of head or leg injuries. Officials said the injuries are not life-threatening. One woman was led away by a paramedic after Saturday’s crash, draped in a red blanket.

The large, coordinated police response to traffic accident reflects the high level of threats Britain has faced this year, including a spate of lethal attacks on London and Manchester, two of which involved vehicles hitting pedestrians.

Britain has been on a ‘‘severe’’ terrorist threat level indicating an attack is viewed as highly likely.

The crash took place on a day when the central London museum district is teeming with pedestrians. Photographs showed a dented silver car and a man being pinned to the ground outside the museum.

London Mayor Sadiq Khan tweeted that he was in close contact with Assistant Metropolitan Police Commissioner Mark Rowley, who plays a lead role in the police counterterrorism operation.

Workers in a cafe near the Natural History Museum said they fled in panic. The musuem closed after the crash but its neighbor, the Victoria and Albert Museum, remained open.

In France on Saturday, a judicial official said three men face preliminary terror-linked charges in the failed attack a week ago on a residential building in an upscale Paris neighborhood with gas canisters that failed to ignite.

The suspects were placed under formal investigation late Friday in the mysterious attack attempt in the building in western Paris’s chic 16th arrondissement, the official said. No motive for the attack has been uncovered, and the three have refused to answer questions.