Crews are still struggling to contain the flames that engulfed the Grade I listed stately home.
A National Trust spokesman said: "We can confirm that a fire has broken out this afternoon at Clandon Park. The building was evacuated and everyone who was in the house is safe. Surrey Fire and Rescue Service is working to bring the fire under control and we would like to thank them for their swift response. We are devastated to see this happen and will update you as we know more."
Nearby resident Phoebe Grant said she saw flames "shooting out of the building"
"They've evacuated the whole area, they won't let anyone near Clandon Park," the 18-year-old said.
"There's still smoke and flames coming from the roof. It looks like part of the roof has caved in."
Another local resident, John Covey, told Get Surrey that fire crews are struggling to control the blaze. The trouble is a lack of water," he added. They can't get enough pressure up there. They had it under control but then the water went down and the flames went up again. It's a disaster."