Police probe fire at Singo's guesthouse

Police are waiting for businessman John Singleton's burnt-out guest house to be declared safe so they can begin investigations.

Detectives are investigating whether any suspicious circumstances surround a fire which destroyed a luxury guest house owned by ad man John Singleton on NSW's central coast.

About 80 firefighters battled the blaze at the prominent businessman's property at Pretty Beach on Sunday night.

They prevented the fire spreading to bushland but were unable to save the guest house from an estimated $500,000 worth of damage.

No one was in the house at the time of the fire.

The Rural Fire Service (RFS) will hand the fire scene over to police later on Monday.

Police said specialist forensics officers and RFS investigators would begin investigations as soon as engineers declared the site safe.