NSW harness racing has been rocked by the report that a horse prepared by leading trainer Luke McCarthy has returned a positive swab.

McCarthy joins a long list of trainers under investigation after a tumultuous change in the Stewards panel late last year.

A sample taken from McCarthy’s horse Mach Wiper has shown traces of the banned steroid boldenone.

Harness Racing NSW issued a statement saying: “A report from the Australian Racing Forensic Laboratory (ARFL) that boldenone, at a level greater than 15 micrograms per litre in urine, has been detected in a post race urine sample taken from MACH WIPER following its win in the NXFM Newcastle Cup (2550metres) run at Newcastle on 9 December 2011.

The “B” sample and the control were sent to the Hong Kong Jockey Club Racing Laboratory (HKJC) for confirmation, and the HKJC has today confirm the presence of boldenone in the post race urine sample taken from MACH WIPER on 9 December 2011.

Trainer Mr Luke McCarthy has been advised of these findings. An inquiry will be conducted at a time and date to be fixed.

Acting under the provisions of Australian Harness Racing Rule 183 (A), MACH WIPER has been stood down until further notice.

McCarthy is currently the leading trainer in NSW with a total of 129 winners for well over $1,300,000 in stakes.

A winner at 24 of his 52 race starts Mach Wiper would have been a serious contender in the 2012 Inter Dominion series which begins at Gloucester Park in Perth on Friday.