Ten spring carnival raiders at the centre of a feed contamination scare have been cleared to race after returning negative test results to Zilpaterol.

It was feared the international horses, from the stables of Irish trainers Aidan and Joseph O'Brien, could have ingested the banned substance through a suspected batch of affected feed.

The father and son trainers scratched runners from races in Europe last weekend after being made aware of the potential issue.

Racing Victoria stewards conducted out of competition testing on the horses, who included the highly-rated Anthony Van Dyck and Melbourne Cup fancy Tiger Moth.

All test results came back negative to Zilpaterol on Friday.