Friends said Cheers, who has for years successfully managed a small team with a unique training method of backing horses up on short breaks, left the Hawkesbury racecourse in her truck on her own around 2pm on Sunday, and was towing four horses.

Police said she was believed to have driven to a service station in Beresfield, in Newcastle's north-west, about 175 kilometres from Clarendon.

The horses were found at the petrol station and have been returned to Taree.

A search has been underway at Beresfield and police are appealing for help from the public to find Cheers.

Cheers' two runners at Hawkesbury, Mister Hootabell and Gumball, finished second last and last respectively

Anyone who sees Cheers has been urged to contact Crime Stoppers on 1800 333 000.