Trainer Jamie McConachy has been found guilty of a cobalt charge and stewards announced an inquiry into cobalt irregularities in two horses of another trainer on Tuesday.

After an inquiry which ran over three days during a month's period McConachy was found to have presented Vandalised with a cobalt irregularity when he won the Rockhampton Cup in June 2014.

McConachy is the second thoroughbred trainer in Queensland to be convicted of a cobalt charge after Glen Baker was disqualified for two years in May.

However, McConachy's charge was retrospective as his offence was found to be committed before the national threshold was announced in January this year.

Baker has appealed his sentence and a decision is expected next week.

At Tuesday's hearing, McConachy's lawyer Matt Tutt argued that cobalt sentences should be no different from other prohibited substance penalties.

He said it would not be unfair to impose a fine rather than a disqualification as his client was a fulltime trainer.

Stewards disqualified Vandalised but decided to adjourn delivering sentence on McConachy until they can give written reasons.

Chief steward Allan Reardon said it was a very important decision which could have an impact on cases Australia wide.

"We believed it wasn't a case where we could just make a decision after 30 minutes of deliberations. We will give our decision in writing so our reasons will be clear," Mr Reardon said.

The decision should be available late this week or early next week.

Meanwhile, Reardon confirmed an inquiry would be opened next week into high cobalt levels found in two horses trained by Rochelle Smith on the Darling Downs.

Reardon said irregularities had been found in Grey Countess from a Gold Coast meeting on May 30 and from Vimzig at Toowoomba on May 16.

"Smith has been advised and we will open an inquiry in Toowoomba next week," Reardon said.