Ruggari has been stood down after stewards reopened an inquiry into a race at Tamworth on September 17.

Ruggari is the trainer-driver of Regal Hawk, which started favourite in the race but was retired shortly after the start with an apparent gear malfunction.

Maitland trainer-driver Mathew Jackson and reinsman Anthony Davies are also on the sidelines while stewards launch a separate probe into circumstances surrounding Premium Red being retired as a short-priced favourite with an apparent gear malfunction shortly after the start of a race at Newcastle on Thursday.

Jackson has been stood down since being involved in an incident in the stabling area at Tamworth on January 24.

Stewards have extended their inquiries to cover all other horses in Jackson's care. They have banned Jackon's horses from racing pending the inquiry.

Chairman of stewards Michael Beattie said the inquiry, which will start today, would seek evidence from Premium Red's connections.

He said their investigations into the race on Thursday had been comprehensive and had uncovered evidence about other races.

The Regal Hawk inquiry will also begin today.

Ruggari has Genuwine engaged in the Interdominion Championship second-round heats at Newcastle International Paceway on Saturday night.

Genuwine is owned by Queensland mining billionaire Clive Palmer.