LONDON >> A car crash that injured 11 people outside a major London tourist attraction today sparked fears of a terrorist attack but turned out to be simply a traffic accident, London police said.

The accident at 2:20 p.m. outside the popular Natural History Museum in the heart of central London brought a gigantic police response, including helicopters and hazardous area response teams, because of terrorist concerns.

Police said 11 people were injured when a car apparently mounted the pavement and hit pedestrians. Nine people were hospitalized with head and leg injuries that were not judged to be life-changing.

Panicky scenes ensued after the pedestrians were struck and it took nearly four hours for police to reassure the anxious public that it was not another terrorist attack.

Britons in general, and Londoners in particular, have been jumpy after a string of extremist attacks this year, including deadly attacks using vehicles to hit pedestrians on Westminster Bridge and London Bridge. Britain has been on a “severe” terrorist threat level indicating that the Joint Terrorism Analysis Center believes an attack is viewed as highly likely.

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

Witnesses described a 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.

Workers in a cafe near the Natural History Museum say they fled the scene in fear.

Marilin Mueller, 20, said she thought at first it was a traffic accident but had doubts when “loads of police cars” arrived.

“All of these police came marching down saying, ‘Move, move.’ They said, ‘you need to evacuate,’” she said.

Dieon Rurora said people were running down the street to get away and some fell.

“It was quite scary,” he said.

One woman draped in a red blanket was led away by a paramedic after the crash. Others were seen leaving with their legs bandaged.

The crash took place on a day when the central London museum district was teeming with pedestrians. Photographs showed a dented silver car and a man being pinned to the ground outside the museum. A police forensics officer in blue coveralls took pictures of the crash site.

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’s counter-terrorism operation.

The Natural History Museum closed after the crash but its neighbor, the famed Victoria and Albert Museum, remained open.

British Prime Minister Theresa May thanked the first responders and the public for their help and said her thoughts were with the injured.