A woman and four emergency workers are being treated in a London hospital after being exposed to a “hazardous substance”.

The woman was taken to Croydon University Hospital by the London Ambulance Service (LAS) after reports she had ingested poison.

Two Metropolitan Police officers and two members of staff from the LAS were exposed to the substance and 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.”

The London Ambulance Service (LAS) has also confirmed two of its members of staff are being treated for exposure to harmful chemicals.

An LAS spokesperson said: “We were called at 03.37 this morning (April 4) in response to a reports of a person unwell in Thornton Heath, CR7.

“We sent an ambulance crew and took a woman to hospital after she was found to be in possession of a possible hazardous substance.

“We sent further resources to hospital including ambulance crews, an incident response officer and members of our Hazardous Area Response Team (HART).

“Two members of staff who initially responded to the patient were treated for exposure to harmful chemicals and are being monitored as a precaution.”

A spokesperson for Croydon Health Services NHS Trust said: “Following an incident in Croydon this morning we have treated a small number of patients, including two police officers, for chemical exposure.

“This was an isolated incident and Croydon University Hospital has remained open for patients throughout.”