They’re apparently known to each other.

Lambeth Borough Commander, Gabriel Cameron has this update on the investigation in Lessar Avenue.

These eyewitnesses explain what they saw.

Statement from LFB:

Firefighters attended a chemical incident on Lessar Avenue in Clapham.

Crews provided immediate emergency care to a woman and child who are believed to have sustained injuries from a corrosive substance which has now been confirmed by the Metropolitan Police to be alkaline. Another child was also treated by crews. Several people, who came to the aid of the woman and child, were also treated at the scene after coming into contact with the corrosive substance. They were all taken to hospital by London Ambulance Service crews.

Assistant Commissioner Pat Goulbourne said: “Firefighters were on scene three minutes after being called to help at this terrible incident. This included specially trained crews and equipment to deal with hazardous materials incidents. Crews quickly treated a number of casualties at the scene alongside emergency service colleagues, whilst identifying the substance.

“A number of people sustained injuries whilst coming to the aid of the woman and children. Injuries caused by corrosive substances can be very damaging and require immediate medical attention. It is important to call 999 immediately and to keep a safe distance from someone you believe to have been exposed to a hazardous substance.

“The Brigade supports the ‘Remove Remove Remove’ general safety narrative by Counter Terrorism Policing, which provides key messaging and advice on what to do in the event of a person becoming exposed.”

The Brigade was called at 1935 and the incident was over for firefighters by 2121. Two fire engines from Clapham and Battersea fire stations attended the scene alongside specialist hazardous materials colleagues.