That is a lesser charge than Victorian trainers Danny O'Brien, Mark Kavangh and Peter Moody, who faced charges of administering cobalt in Australia. Kavanagh, a Melbourne-Cup winning trainer, was disqualified for four years and O'Brien for three years. Moody's case has not been heard.
O'Sullivan called the announcement of the charges a "huge relief" to himself and Scott.
"If I was done for administering then that is a serious charge, but this is not administering... we've been charged for presenting ... the horses went to the races with something in them that we were not aware of."
The two Matamata trainers have three horses under investigation. They are Sound Proposition, Quintastics and Suffire.
The cobalt threshold in racing is 200 micrograms per litre of urine. Sound Proposition was swabbed after running third in the New Zealand Derby at Ellerslie in Auckland in February last year.
The Racing Integrity Unit (RIU) said he returned 541. It also said Quintastics had a reading of 640 when tested after winning at Matamata in March last year. Suffire registered 309 from a swab following her win at Tauranga in February last year.
The RIU issued a press release yesterday explaining why it charged O'Sullivan and Scott, who will now be subject to an upcoming hearing in front of the Judicial Control Authority. If found guilty, they face five-year bans or disqualification and a fine as high as $25,000.
It alleged the pair committed three breaches of Rule 804 (2) of the New Zealand Rules of Thoroughbred Racing. It also said the circumstances surrounding the cobalt positives in New Zealand were "significantly different" to the recent Australian cases.
The RIU said O'Sullivan's Wexford Stables operation had said the horses had been exposed to "heavily cobalt-dosed water troughs the horses shared with dairy cattle".
In June last year, Wexford Stables posted on its website: "We are totally mystified by the positive result within our stable. We operate an extremely rigid regime to ensure that none of our horses races with a prohibited substance in its system. Our priority is to undertake a comprehensive review of our training and feeding processes, so that we can reassure all our owners that we are doing everything possible to ensure compliance with the rules of racing, including assisting, where we can, the RIU with its investigations."
A series of RIU trials proved that levels above 200 can be caused by the oral feeding of cobalt in high concentrations. The trials were carried out by the RIU's adviser, who is a vet, and were peer reviewed by an international expert on the subject.