Nine people, including two children, have been injured in an incident involving a "corrosive substance" in Clapham, south London.
"Three victims - a woman and her two young children - have been taken to hospital for treatment," the Metropolitan Police said in a statement on Wednesday.
Three other people - all adults - were taken to hospital for injuries.
Three officers were also taken to hospital with minor injuries, the statement said.
There have been no arrests at this stage.
"Firefighters were called to a chemical incident on Lessar Avenue in Clapham this evening," the London Fire Brigade said in an emailed statement to Reuters.
Crews used specialist equipment to detect a corrosive substance believed to have been used, it added, without giving any further details.
