Children and teachers were evacuated from a school after a suspected explosion caused a fire to break out.
Eyewitnesses reported hearing the blast, at St George's Junior School in Weybridge, Surrey, at about 12:35 GMT.
Shortly afterwards, huge clouds of black smoke were seen billowing up from building works on the school grounds.
All children and staff were later allowed to return inside the school, and no injuries were reported, Surrey Police said.
An eye witness said he had been told there were no casualties but had seen children being evacuated.
'Black and billowing'
"I saw all of them collected together in a road behind the school there were teachers making sure they didn't go anywhere," he said.
"They were safe away from the fire. The smoke was blowing away from them."
"It was black and billowing but the fire crews are down there and they have obviously dealt with it."
'Returned to class'
Head teacher Antony Hudson said he was relieved there had been no casualties.
"All the children have returned to class and we very much look forward to seeing them again on Monday morning for business as usual," he said.
Surrey Police said several roads had been closed and advised motorists to avoid the area.
Parents should await further updates before attempting to collect their children, the force said.
A spokesman for Surrey Fire and Rescue Service said 40 firefighters, eight fire engines and a number of specialist vehicles were sent to the blaze.
Area commander Ian Thomson said the roof was well alight when crews arrived.
"The fire is now under control and we are investigating the cause," he said.
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