Len Treloar and Jamie McConachy have been named as the two Queensland thoroughbred trainers to have horses return illegal levels of cobalt.

However, Racing Queensland has been unable to contact Treloar who is no longer licensed after closing his business in July saying it was not financially viable.

Treloar, who began his career in Melbourne 30 years ago, opened stables at Caloundra in 2010 after several successful years in Singapore.

The Treloar-trained In The Sky Rocket returned an elevated level of cobalt after he ran second at Doomben in March last year.

Three harness trainers - Shawn Grimsey, Trevor Lambourn and Ken Belford - face stewards inquiries along with McConachy.

The McConachy-trained Vandalised returned a high cobalt level after his win in the Rockhampton Cup in June.

Grimsey and Lambourn had two horses each return samples above the allowable 200mcg per litre of urine while Belford had one.

Victorian trainers Peter Moody, Mark Kavanagh, Danny O'Brien and the father-son partnership of Lee and Shannon Hope are the subject of an investigation into high levels of cobalt from horses in their care.

Newcastle trainer Darren Smith will find out his fate on Friday with Racing NSW stewards to hand down a penalty after finding him guilty of more than 40 cobalt related charges.

Cobalt is an essential mineral but can alter a horse's blood pattern and has been found to be toxic in high levels.