A substance found in trainer Paul Murray's stable fridge contained cobalt at a level previously not seen by Racing NSW stewards.

Murray faces eight charges relating to high levels of cobalt found in pre-race swabs taken from Alma's Fury before he won the Apollo Stakes in February 2013 and ran second in the Doncaster Prelude in April that year.

The stored samples were analysed after Racing NSW compliance officers found a bottle labelled Concentrated Trace Minerals during a routine race-day inspection of Murray's stable in June, 2014.

Murray denied any knowledge of that particular bottle, telling stewards on Thursday he had used another bottle with the same name given to him by stable client Peter Holz, a man he said owed the stable around $80,000.

Photographs taken on the day Racing NSW visited the stable showed the bottle sitting in front of a bag of prawns the trainer said he had put there earlier that morning.

"It wasn't there when I put the prawns in the fridge," Murray said.

"The other bottle was different and had a different-coloured label.

"Peter Holz got it for me and said everyone was using it so I added it to the drips."

Racing NSW chief steward Ray Murrihy said analysis of the bottle found in the fridge showed extraordinary cobalt levels.

"It had double the concentration of any cobalt product we have ever seen," Murrihy said.

The reading from Alma's Fury's blood sample was 391mcg and a urine sample returned 940mcg.

Stewards have been unable to locate Holz but have telephone records indicating multiple calls between him and disqualified harness racing trainer Shannon Wonson, the person named as supplying Darren Smith with a cobalt product.

Smith is serving a 15-year disqualification after many horses in his stable returned high cobalt levels.

Murray said Wonson had been to his stable to swim horses but he told him not to return.

"I found out he was in trouble and told him not to come back," he said.

Although the national cobalt threshold of 200mcg/L was not in place until January last year, Racing NSW successfully prosecuted Smith on the basis cobalt comes within the rules prohibiting substances which affect the blood system.

Murray did not enter a plea to the charges and stewards will examine data on his phone before the inquiry resumes in February.