Dozens of firefighters spent hours tackling a blaze at a large primary school in east London.
Twelve fire engines and about 80 firefighters were called to Roding Primary School, Dagenham, shortly before 05:00 BST and had the fire under control by 07:49.
The Metropolitan Police said there were no reported injuries.
About half of the school building has been damaged. The cause of the fire is not yet known.
According to the school, it is "one of the biggest primary schools in the country".
Pupils were due to return on Wednesday following the summer holidays.
'Working with schools'
The school, which has just under 1,300 pupils, has two sites - one on Hewett Road, where the fire was, and another on nearby Cannington Road.
In a statement, the school said the Cannington Road site will open as usual on Wednesday but the Hewett site had been deemed not safe and would remain closed for the rest of the week.
"We will update Hewett parents as soon as we can about a re-opening date when we have a better idea," they said.
Earlier, Barking and Dagenham Council said it was "working with local schools and Roding Primary School" to accommodate the 378 pupils who attend the Hewett Road site.
Nearby St Teresa school was due to reopen but has remained closed as a precaution, following the advice from the London Fire Brigade (LFB). It will open as usual tomorrow.
LFB said crews from Dagenham, Barking, Ilford and surrounding stations made "steady" progress in tackling the fire throughout the morning after being called at 04:50.
The blaze is under control but LFB expect firefigthters to remain at the school for the rest of the day.
LFB station manager Rod Wainwright said the brigade was alerted by an automatic fire alarm.
"When we arrived crews were met with a significant fire," he said.
"We have had no reported injuries at this time and believe the school was empty.
"It is unfortunate timing that this fire has occurred just before the start of term."
Mr Wainwright added: "It is too soon to speculate on the cause of the fire but as soon as they're able to, fire investigators will enter the site to start their work."
The brigade's Deputy Assistant Commissioner, Lee Drawbridge, said the building may have been saved had it been fitted with sprinklers.
"London's firefighters are called to more than 80 fires in schools every year and in most cases, sprinklers are not fitted - meaning millions of pounds are wasted repairing fire and water damage," he said.
At the scene: Greg McKenzie, BBC London
As I got closer to Dagenham you could see the huge plumes of smoke billowing into the air.
The front of the school was on fire and firefighters told people to move back. People living nearby were advised to shut their windows as the smoke was quite thick.
However, some neighbours - in their dressing gowns and slippers - still looked on.
Although there was a sense of calm, I have spoken with some schoolchildren and parents who were really worried. Some of those who worked at Roding Primary were in a state of shock.