Superintendent Gabriel Cameron said none of their conditions were life-threatening, but the injuries could be life-changing.
A 31-year-old woman and her three-year-old daughter have been seriously injured after corrosive acid was allegedly thrown onto them on Wednesday in the south London borough of Clapham.
At least other nine people, including an eight-year-old girl, were injured in the same attack, the Metropolitan Police said.
Both the woman and the children were taken to hospital, as were three other people who were injured after coming to their aid, Scotland Yard said in a statement.
Detective Superintendent Alexander Castle said three police officers were also taken to hospital after arriving at the scene in Lambeth, but their injuries were minor.
Castle said tests were underway to determine what had caused the injuries, but “at this stage we believe it was a corrosive substance”. The police are still searching for the attacker who was seen fleeing the scene.
The police air service is taking part in the operation, for which the public has also been asked to help.
Marina Ahmad, a member of the London Assembly, said that both the women and the injured girl were passengers in the car.
The CCTV footage shows a man running around a car before getting into the driver’s seat. A woman and her child are sitting in front of the car.
The images show the car running over the woman and then the man stopping the car, getting out and aggressively grabbing the child.
After the incident, the man tried to flee the scene in his car, but collided with another vehicle and left on foot.
“While none of their conditions are life-threatening, the injuries to the woman and the younger girl could be life-changing,” said Superintendent Gabriel Cameron.
“It may be some time before hospital staff are able to say how serious this could be,” he added.
One of the witnesses told Sky News what he saw: “The man grabbed one of the two children violently and slammed them on the floor”.
“The lady then screamed: ‘My eyes! My eyes! Call the police, my eyes! Then I saw him run away. It was all so traumatising”.