Fire engulfs waterfront Gold Coast mansion

Investigations are underway after a Gold Coast mansion went up in flames.

The fire erupted at about 12.40pm on Rannock Avenue, with neighbours racing to stop flames spreading.

Neighbour Matt Nosic fought to stop the flames jumping on to his home.

"I was hosing my roof and next door as well," he told 9News.

Other neighbours ran to see if anybody was home — luckily, nobody was.

But within half an hour the mansion was rubble.

"It took off very, very quickly, as you can see, it was already through the roof," Graeme Stoner from Queensland Fire and Rescue said.

The cause of the blaze is as yet undetermined.