Champion Irish trainer Aidan O'Brien and his family have escaped unharmed after a fire at their Ballydoyle home.

The blaze is reported to have started in an upstairs bedroom at around 10pm on Wednesday (0700 Thurs AEST) but the emergency services were soon on the scene.

A Garda spokesman said people were in the house at the time but escaped unharmed.

The roof was extensively damaged before several units of the fire service brought the blaze under control.

Investigations are continuing but the cause of the fire is not believed to be suspicious.