Bindi Cheers,  44, was last seen at the track on Racecourse Road in Clarendon about 2pm on Sunday, but never returned to her home in Taree, on the Mid North Coast of NSW, police said.

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 racecourse in her truck on her own, 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 on Enterprise Drive, but there was no sign of Cheers.

"Bindi would never leave her horses like that," one person who knew Cheers wrote on social media. The alarm was raised when Cheers did not return to Taree, and police began searching for her late on Sunday. The search resumed early on Monday morning.

Police said Cheers was believed to be on foot.

She is described as being about 175 centimetres tall, with a slim build and a fair complexion.

She was last seen wearing grey cargo pants, running shoes, and may be wearing a maroon jacket.

The horses have since been returned to Taree.

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