Western Australia's racing authorities say they have ruled out any corruption in the industry after allegations of race fixing.

The allegations involve jockeys in several races in Perth and across the state.

A letter sent last month to local racing authorities was revealed on Thursday by the West Australian newspaper.

The letter alleged a group involving eastern states betting syndicates had manipulated knowledge of five races since December.

The anonymous letter named four jockeys who the writer believed were involved in the races, which did not include any of WA's major spring carnival events.

Richard Burt, chief executive of Racing and Wagering WA (RWWA), said the allegations had been internally investigated and they were satisfied nothing untoward had occurred.

"The writer claims that races are rigged and jockeys are being paid for their services for the betting outcomes, primarily in metropolitan races," Mr Burt told ABC radio.

"We have gone back over all the footage with a fine-toothed comb and they (stewards) don't believe the allegations that are (made) in the letter are warranted.

"We have treated it as seriously as we can. We have had a panel of stewards go over each of the races alleged and over the specific riding tactics.

"We believe the conduct of the races has gone in accordance with the rules of racing."

However, Mr Burt did admit none of the named jockeys had been interviewed as part of the investigation.

"The most objective way of looking at a race is looking at video, so you can actually see what is going on rather than have perceptions," Mr Burt said.

Mr Burt said the RWWA would now be seeking out owners, trainers and jockeys to conduct further inquiries.