It is understood leading country trainer Lee Hope had one of his team return an irregularity.

NSW Trotting was the first code to discover use of cobalt chloride, and on Friday in Sydney trainer Darren Smith faces a number of charges for its illegal use.

Racing Victoria chief steward Terry Bailey would not comment on the matter when contacted by Fairfax Media on Thursday.

Earlier this year Bailey said he and overseas stewards were on high alert and were extensively testing for cobalt chloride, but he admitted no test threshold existed at that time.

Bailey, unlike stewards in Sydney, has now implemented a threshold of 200 micrograms per litre of urine.

While a number of cobalt charges will be investigated in the Sydney inquiry, the difficulty will be that it has no threshold.

Concern in Victoria and the US that cobalt chloride could have the same effect as EPO – or blood doping – was the main reason for installing a threshold in Victoria.

Victorian investigators now use testing laboratories in Sydney and overseas in a bid to apprehend trainers who are using the drug.

Cobalt chloride is not a prescription medication, so it can be easily obtained, although there are reports it is currently in short supply in Australia.

In the US, the owners of the Meadlowlands racetrack in New Jersey banned two trainers after some of their horses were found to have elevated levels of cobalt chloride.

In one intriguing case, world-renowned trainer Bob Baffert, who prepares his horses in California, had seven of his horses die, with a strong suspicion cobalt chloride was the cause.

Cobalt chloride makes the body feel it is not receiving enough oxygen, which results in it producing more EPO, the hormone responsible for controlling blood cell reduction.

Excess EPO production has been linked with the deaths of several athletes and cyclists since the 1980s.