Japanese racehorse Tosen Stardom is at the centre of an inquiry that threatens his place in the Queen Elizabeth Stakes.

Racing NSW stewards launched an investigation on Tuesday when it was reported Tosen Stardom had blood in both nostrils following a track gallop at Canterbury.

If the horse is declared a bleeder, Tosen Stardom will be given a three-month ban from competing under Australia's rules of racing.

The only northern hemisphere-trained horse in Sydney for The Championships, Tosen Stardom underwent an endoscopic examination at the Canterbury Park Quarantine Centre.

Along with photographic exhibits, the results of the endoscopy have been sent to Tosen Stardom's Japanese owners and their vet, Dr Tomonori Tosusa.

Dr Tosusa gave evidence via a telephone hook-up with stewards.

Tosen Stardom's connections have been asked to make submissions before the inquiry resumes on Thursday.

A five-year-old, Tosen Stardom is making his second trip to Sydney after a placing in last year's Ranvet Stakes before a midfield finish in the Queen Elizabeth Stakes won by Criterion.

He is the last horse standing among Japan's original representation for The Championships after Isla Bonita, Logotype and Tosen Reve failed to make the trip because of injury and indifferent lead-up form.

Tosen Stardom arrived in Sydney last week and had been rated a $15 chance to win the Queen Elizabeth at Randwick on Saturday week.

Stewards have asked betting agencies to suspend betting on the $4 million race until their inquiry is finished.