Firefighters have been battling a blaze at Chessington World of Adventures Resort in Surrey.
The London Ambulance Service said it received a call about the fire at 9am and sent emergency response crews to the scene.
The park was due to open at 10am for a "festive zoo day" according to its website, but has now been closed for the day.
Eight fire engines are on the scene of the fire at the Creaky Cafe.
The park said on Twitter: "Due to unforeseen circumstances Chessington will be closed today.
"If you had tickets booked for today, they will be valid for another day in the future... Further updates will follow."
London Fire Brigade said the park was not open to the public when the blaze started and no one was believed to be injured.
A Metropolitan Police spokesman said: "There are some road closures in place to ensure people are kept a safe distance away."
Surrey Police said people should avoid the area around the park as the A243 was closed. Source