DR Brian Stewart, the chief Racing Victoria veterinarian, has heard the swelling rumours, but denied tests have revealed Admire Rakti had a prohibited substance in its system, reports Racing Network.

Dr Stewart said extensive testing at the University of Melbourne veterinary hospital remain on-going.

He said RV is committed to “full transparency” in whatever the tests uncover.

Admire Rakti, the favourite for the Melbourne Cup, collapsed and died in its tie-up stall about 15 minutes after finishing last.

Preliminary autopsy results indicated the horse died of heart failure.

Asked if a prohibited substance had been discovered in Admire Rakti during the autopsy, Dr Stewart replied: “That’s the rumour going around, but it’s incorrect.

“The tests are still on-going. We are going through it with a fine-tooth comb as we do with all sudden deaths.

“Some of the tests are quite complicated and do take time. The samples are not cleared yet, but I can tell you definitely there’s been no positive detection.”

Dr Stewart said one of the tests being carried out is for insulin, but noted there is “no sign or evidence of it yet”.

“We’re doing a lot of testing so when we do finally tick things off we won’t be leaving things off.

“We want to finish everything before we make any announcements.

“If there was anything we are committed to full transparency, it will be announced.”

Racing Victoria chief steward Terry Bailey said he was still awaiting test results from the autopsy and nothing untoward has been detected.

“We are hearing the rumours but nothing has changed from last week,” he said.

“Three different laboratories are involved in the testing, it is out of our hands at the moment and we are just waiting on the results.

“We were advised that it would be three weeks before the results are in, that was a week ago.

“Once they are in, we would be in a position to release a full report in to the horse’s death.”