The horses tested for possible drug contamination when travelling from Christchurch to the Harness Jewels meeting in Cambridge have all returned negative results.

The horses are therefore all clear to start in their respective events at the Jewels on Saturday.

The New Zealand Racing Board has reopened betting on the six affected races.

“The RIU is very pleased with the result. The integrity system worked as it should. The trainers were proactive in advising the RIU of the potential contamination. The process then put in place by the RIU, working in conjunction with the New Zealand Racing Board, Harness Racing NZ and the Racing Laboratory was transparent, ensuring the public were fully informed and could have confidence in the integrity system," said RIU General Manager, Mike Godber.