The cordon near to a house that collapsed in Thornton Heath after an explosion and fire has been enlarged.

The cordon in Galpin’s Road has been extended to 200 metres at the request of the Health and Safety Executive – which has detected elevated gas readings in the area.

London Fire Brigade said it has one engine standing by and at this stage it hasn’t been called to reports of a gas leak.

The incident, which happened on Monday morning, has been described as a “gas explosion” by the leader of Merton Council Ross Garrod.

London Fire Brigade said enquiries are ongoing to determine the cause of the explosion.

A four-year-old girl died and three people are in hospital with injuries which are “potentially life-threatening”.

A fourth person was treated at the scene.

Police are knocking door to door to inform residents of the extended cordon and to provide further support.

More than 100 people have now been evacuated from the area and the New Horizon Centre in Mitcham is being used an evacuation centre.

Residents can be provided with help regarding future accommodation, financial help, food, as well as emotional support at the centre.

A clothing donation station has also been opened at the Ascension Church on Sherwood Park Road.

The Council asks that any residents who are able to donate adult and children's clothes to drop donations there.

Merton Council has also announced Southern Gas Networks are continuing to work on the site and advises that people stay away from the cordon while checks are ongoing.

A spokesperson for Southern Gas Networks said: "We can confirm that our engineers are currently responding to the incident in Galpin’s Road, Thornton Heath.

"To ensure the safety of local residents, a number of properties were evacuated in the local area earlier today.

"We are working with Merton Council and other local partners to provide temporary accommodation and ongoing support to those affected."

A spokesperson for Merton Council said: “Following further inspection by the Health and Safety Executive on site this morning, the cordon is being extended to 200m, and we are in the process of evacuating further homes on Galpin’s Road.

“Officers are knocking door to door to advise and help residents.

“Southern Gas Networks continue to work on site, and residents must stay away from the cordon area until it is safe to return.

“Council officers are working as hard as possible to help the 100-plus residents who have been evacuated, and will continue to do so today, as more homes are evacuated.

“New Horizon Centre continues to act as our evacuation centre and is offering support including onward accommodation, financial help, food and emotional support.

“Additionally, a clothing donation centre has been opened at the Ascension Church on Sherwood Park Road – any residents able to donate clothes (adult and children) are asked to drop donations there.

“We will continue to update this statement as more information is available.

“Alternatively, follow our Twitter channel @Merton_Council.”

A London Fire Brigade spokesperson said: “The cordon has been extended to 200m at the request of the HSE, which has detected elevated gas readings in the area.

“We have one fire engine there just standing by and at this stage, haven’t been called to reports of a gas leak.”

We have asked the Metropolitan Police for more information.