Police are investigating the death of a seven-year-old boy in Surrey reported to be linked to the pumping out of flood water from his home.
Officers were called to a property in Thameside, in Chertsey, Surrey, during the early hours of this morning.
The three occupants were subsequently taken by ambulance to hospital, a spokesman for Surrey Police said.
The boy was later declared dead. A man in his 40s, believed to be his father, and a woman in her 30s, who is understood to be his mother, are in a serious condition but it is not thought to be life threatening.
Fifteen people, including police officers, were also taken to hospital as a precaution and nearby properties were evacuated.
Chief Superintendent Dave Miller said the cause of the illness was unknown, amid speculation that carbon monoxide poisoning may have been to blame.
He said: "It is very sad that a young child has died earlier today. Our thoughts are with his parents who are currently ill in hospital.
"Police officers are currently with them and we will continue to offer our support during this difficult time .
"Our aim is to keep people safe and find out the cause.
"I would like to reassure local residents our officers are working closely with partner agencies and a full and thorough investigation is currently under way to determine the circumstances around this tragic incident.
"We are currently following various lines of inquiry and it would be wrong to speculate on the cause of death at this stage.
"The cause of the illness is currently unknown but what I can confirm is that the people who were taken ill are from a very localised area.
"We cannot rule out that there may be a link to flooding in the local area and whilst the investigation is ongoing local residents should follow sensible precautions."
The area where the incident occurred has been affected by flooding, and Mr Miller told reporters that the weather was "one line of inquiry" they were pursuing in relation to the boy's death.
He urged anyone living in the area, who is feeling unwell and showing signs of diarrhoea and fever to seek medical help.
A police guard remained at the location and road closures were in place. The coroner's office has been told about the boy's death.
A South East Coast Ambulance (Secamb) spokeswoman said the boy was found to be in a "very serious condition" when crews arrived.
She said it was unclear what caused the illness and was unable to be drawn on suggestions that carbon monoxide poisoning was to blame.
Local resident David North, who works in Chertsey, said he saw a yellow hose hanging from the ground-floor front window of the property at the centre of the alert.
Mr North, 45, said: "I was taking photographs of the flooding in the local area. As I turned up, there was a higher-than-normal police presence.
"Officers were blocking direct access to some of the roads and they were being quite forceful about where you could and couldn't go.
"I saw a yellow hose coming from the front window on the ground floor. Whether it was pumping out water or something else, I don't know.
"My understanding is that this incident was found out while evacuations were being carried out due to the flooding."
Additional reporting by Press Association