Two Metropolitan Police officers exposed to the substance are under observation.
A woman and two police officers are being treated in a London hospital after being exposed to a “hazardous substance”, the Metropolitan Police said.
The woman was taken to Croydon University Hospital by the London Ambulance Service (LAS) after reports she had ingested poison.
Two Metropolitan Police officers exposed to the substance are under observation.
Parts of the hospital were initially closed off, but the incident has since been stood down.
A police spokesperson said: “Police were called at 03:46hrs by London Ambulance Service to reports of a woman having ingested poison at an address in Thornton Heath.
“The woman was taken to a south London hospital by LAS where she was found to be in possession of a possible hazardous substance.
“Officers and the London Fire Brigade attended Mayday Hospital and safety cordons and closures were established while specialist officers examined the item and safety procedures were enacted.
“Ambulances and emergency vehicles were given access to the hospital throughout the incident response.
“Road closures have since been lifted and the incident stood down.
“There were no arrests.”
