The Queensland Racing Integrity Commission has launched an independent inquiry into how the wrong horse was allowed to start in a race at Rockhampton.

Trainer Julieann Lancaster had several runners at Thursday's meeting including Authadane in the Benchmark 60 (race six) and Plain 'N' Simple in the Class Six (race seven).

Plain 'N' Simple was allegedly saddled as Authadane and ran in the Benchmark race in which he finished sixth.

He ran after he was mistakenly passed in the enclosure branding test.

The mistake was discovered when it was time for Plan 'N' Simple to be saddled and stewards were alerted.

At an inquiry, Lancaster said she had saddled the incorrect horse for race six as she was of the opinion that Plain 'N' Simple was to race in the event and Authdane was engaged in race seven.

Lancaster pleaded guilty to a charge that her negligence in failing to correctly identify Authadane as the horse engaged in race six had led to a breach of rules.

After hearing submissions on penalty, stewards adjourned but Authadane was disqualified from the event while Plain 'N' Simple was a late scratching from the Class Six race.

QRIC's acting commissioner, Mark Ainsworth, confirmed QRIC would carry out an independent investigation into the incident as well as the stewards inquiry.

"A steward's Inquiry was opened into the incident on Thursday and has been adjourned pending further investigations," he said.

"The commission takes these incidents seriously and the independent investigation and the stewards inquiry will be thorough."

Results of the investigation are expected next week.