Victorian trainers Steven Pateman and Belinda Dunn are both being investigated after each had a horse return illegal cobalt levels.

Racing Victoria stewards are continuing their investigations into the high readings, both of which were above the allowable 100mcg/L.

Steeplechaser Sir Walter Scott, trained by champion jumps jockey Pateman who holds a dual licence, was pre-race tested at Coleraine on September 23 while the Dunn-trained Margot's Boy had a high reading after winning at Tatura the following day.

The initial testing was carried out by Racing Analytical Services Limited while the Racing Science Centre Laboratory confirmed the findings in the reserve portion of the sample.

Cobalt is an essential mineral nutrient which affects multiple body systems but is toxic at high dosages.

It is a prohibited substance in accordance with the Rules of Racing at a concentration in excess of 100 micrograms per litre in urine.