Queensland's integrity chief Ross Barnett says he is disappointed by the number of positive results from random drug and alcohol testing at tracks throughout the state.

Barnett says while it is encouraging that 95 per cent of participants have been doing the right thing, some continue to break the rules.

The Queensland Racing Integrity Commission Integrity Investigations Team has carried out 559 human urine samples and 127 breath tests from thoroughbred and harness racing participants.

Barnett says the no-notice testing operation is an important part of the work of the Commission and of the 155 jockeys, 41 apprentice jockeys and 292 track work riders registered in Queensland, most had been tested at least once during the period.

Confirmed positive results to prohibited substances were found in 14 thoroughbred participants, including to THC, oxazepam, temazepam, cocaine, acetazolamide, ketamine, norketamine, dehydronorketamine, amphetamine, methamphetamine, zopiclone, morphine and codeine, and four participants returned alcohol readings in excess of the permitted .02 threshold.

The latest positive screen was taken at Marburg track work on Tuesday when a harness trainer/driver was stood down after returning an alcohol reading above .02 and screening positive for benzodiazepines.

He was the only harness racing participant to screen positive since July 1.

Other positive screens awaiting confirmatory analysis include ones for THC, methamphetamine and amphetamine, opiates and benzodiazepines.

In the period since July 1, there have been seven instances of participants who failed to provide samples.

Two participants have since faced the stewards, resulting in one disqualification and one suspension.

There has also been six occasions involving three participants who substituted their samples and all three have been disqualified. One case is being finalised by the stewards.