Racing Victoria stewards have decided not to charge trainers Darren Weir and Clinton McDonald after horses in their care returned positive samples to a banned substance.

The Weir-trained Signoff and McDonald's Rib Eye tested positive to ibuprofen after wins in December and January.

In deciding not to charge the trainers, stewards took into consideration the fact they had proactively undertaken elective testing via Racing Analytical Services Limited before the horses raced.

Signoff returned a positive test after winning at Caulfield on Boxing Day while Rib Eye had two positives, firstly after winning at Terang on December 7 and again at Flemington on New Year's Day.

RV stewards have applied to the Racing Appeals and Disciplinary Board to have the horses disqualified from their races.