A woman has been arrested after two sets of twin boys, aged three and four, died in a devastating house fire in south London.

The 27-year-old has been held on suspicion of child neglect, the Metropolitan Police said.

Fire crews were called to a mid-terrace house in Collingwood Road, Sutton, shortly before 7pm on Thursday and found a “very well-developed” blaze, with the four boys inside, said Richard Mills, deputy commissioner of the London Fire Brigade.

He told reporters at the scene on Friday: “I can confirm that they are two sets of twins, ages four and ages three.”

Asked if anyone else was in the home, he said: “On arrival there were four children in the house.”

Scotland Yard said the boys were all related.

They were treated at the scene before being taken to two south London hospitals where they were pronounced dead.

In a statement on Friday, the force confirmed the arrest and said the woman remains in police custody.

Mr Mills said firefighters in breathing apparatus entered the home, removed the four children and gave them CPR.

The fire was under control by 8.36pm and the cause is under investigation.

Speaking of the firefighters involved, he said: “Entering a building and rescuing life is always a very difficult place to be. The age of the children, the fact they are so young, will have a profound impact on them.”

Crews who attended are receiving counselling, he added.

London Fire Commissioner Andy Roe also earlier said the children’s deaths had “left everyone numb with profound sadness”.

Floral tributes were being laid outside the police cordon on Collingwood Road on Friday morning, with a message on one bouquet reading: “To Kyson Bryson Leyton + Logan. Sleep well. Love Grandad.”

Police officers were seen going in and out of the property, where the once-white facade was blackened.

The Metropolitan Police said the children’s next of kin are aware and will be provided with specialist support.

Superintendent Rob Shepherd said on Thursday: “The thoughts of everyone at the South Area Command Unit are with the family and friends of these four young children, who have suffered such a devastating and tragic loss tonight.

“I know these sentiments will be shared by the local community, Sutton and London as a whole.

“We remain on scene with our emergency service colleagues and will be working through the night and beyond. At this very early stage the cause of the fire is unknown and will be investigated.”

The four children who died in the fire were “so well behaved” and “polite”, according to a woman who works at a nearby shop.

The 24-year-old, who did not want to give her name, said the two sets of twin boys often came to her shop with their mother.

She said: “They were always all holding hands, they were so well behaved, so polite.”

The Rev Frances Arnold, priest of the local St Nicholas church, said: “It’s a great shock and tragic loss of life, young children, and so we’ll continue to offer our prayers for the family, the friends, the community here, the emergency services”.

Matt Gray, manager of Sutton United football club, laid yellow-and-black team scarves outside the police cordon at the scene.

He said it was “such a tragic event to happen on our doorstep” and “a huge shock and obviously very devastating”.

Westbourne Primary School in Sutton said they were “devastated” by the deaths of the children, two of whom were pupils there.

In a statement, the school said: “Westbourne Primary School and its entire community are devastated at the news of the tragic loss of the four children; our hearts, thoughts and prayers are with the family and anyone else affected by this heartbreaking event.

“We will continue to support the children, the staff, the families and the community through these very difficult times.”

Home Secretary Priti Patel tweeted: “My thoughts and prayers are with the families and loved ones of the four young children who tragically lost their lives in the fire in Sutton yesterday.

“I am being kept updated by the emergency services and I would like to thank them for their work in such sad circumstances.”