Queensland stewards have renewed their warning about the dangers of arsenic in wood products after a horse trained by Frank Phillips returned a positive swab.

The veteran Caloundra trainer was charged with bringing D'Leeajet to the Sunshine Coast races in May last year with arsenic in her system above the prescribed threshold.

Phillips pleaded guilty to the charge which was his first in more than 60 years as a trainer.

Because of the unusual circumstances and Phillips' good record, the trainer was not penalised but the mare was disqualified.

Chief steward Allan Reardon said stewards took into account a study by the Melbourne University faculty of Veterinary Agricultural Sciences which examined the ingestion of wood shaving containing arsenic and the elevated levels achieved.

"We considered evidence of the analysis of timber post samples taken from the yard in which D'Leeajet was housed and a report from Symbio Laboratories, which confirmed the presence of arsenic in the treated timber," Reardon said.

"Stewards also accepted that when the stable inspection was conducted, photographic evidence confirmed that D'Leeajet had eaten a significant amount of this timber."

"Stewards, therefore, could not exclude to the requisite standard that the level of arsenic detected was not the result of D'Leeajet consuming the timber from the posts."

It was the fourth arsenic case in Queensland in the past month in which stewards have used the Melbourne report.

"We repeat our warning to trainers about shavings and fence posts which have been treated by arsenic," Reardon said.

"Unfortunately, there are more cases to come in thoroughbred and harness racing."