Police first described the incident in the South Kensington area of west London as a collision and said the motive for the incident was under investigation. After updating that they were not considering the possibility that the crash was an act of terrorism, they later recanted and said that they "are keeping an open mind" and looking into all possibilities.
Police later said that the crash was the not terror-related, but a road traffic accident.
A BBC reporter at the scene initially said she could see a car diagonally across the road surrounded by a crowd of people with one or two on the ground. She said she was told by police injuries sustained were minor.
Immediately following the incident, the museum said on Twitter that it was working with police after "a serious incident" outside and would provide more information later. A spokesman told Reuters that no one was being allowed into the building and people were being let out through a different exit.
Britain is on its second highest security alert level, meaning an attack by militants is considered highly likely. There have been five attacks described by the authorities as terrorism this year, three involving vehicles.
The Natural History Museum is the fourth most popular tourist attraction in the United Kingdom, with 4.6 million visits during 2016, according to the Association of Leading Visitor Attractions.
In September, a bomb attack in London's underground system that injured 29 people was claimed by ISIS. During the attack, a home-made bomb on a packed rush-hour commuter train in London engulfed a carriage in flames, though it had failed to fully explode.
During the September attack, passengers on board a train heading into the capital fled as fire engulfed a carriage at Parsons Green underground station in West London, with some suffering burns and other injuries in a stampede to escape, witnesses said.
In June, three Islamist militants drove into people on London Bridge before stabbing people at nearby restaurants and bars, killing eight. The same month, a van was driven into worshippers near a mosque in north London which left one man dead.
In March, a man drove a car into pedestrians on London's Westminster Bridge killing four before stabbing a police officer to death in the grounds of parliament.