Police needing more witnesses to come forward following serious assault in Mareeba.

Detectives investigating the serious assault of a man at the Mareeba Rodeo Grounds, Kerribee Park on Wednesday night (July 10) are appealing for witnesses of the incident to come forward.

Around midnight, following an altercation, a man was attacked and located unconscious at the rodeo grounds on Mareeba Dimbulah Road.

The victim, a 35-year-old man from Ayr, is currently in the Townsville Hospital in a critical condition.

Investigators are urging anyone who may have heard a loud disturbance at the rodeo grounds (showgrounds) between 11pm and midnight, or anyone who may have images or footage of a disturbance to contact police.