Police said two people were stabbed in the incident at a Cookstown GAA game on Thursday evening.
A man, aged in his 40s has been arrested and will be taken to custody for questioning.
It happened at around 9pm at Padráig O’ Cuilinn Pairc on Covent Road in Cookstown during an under-16 championship match between Cookstown Fr Rocks GFC and Fintona Pearses.
Social media footage of the aftermath showed police handcuff a man before leading him away.
Scores of people including many children can be seen around the pitch.
Police said one man was stabbed and taken to hospital while another received treatment at the scene.
In a statement Cookstown Fr Rocks said: "Following a very serious incident at Padráig O’ Cuilinn Pairc this evening during an Under 16 Championship match our thoughts are with the individuals impacted by it.
"The committee will now work to ensure that children and young people who witnessed this disturbing and very serious incident have the support and assistance that they require in the coming days.
"The club will be making no further comment on this."
The Ambulance Service said it received a 999 call at 9.03pm following reports of an incident in the Convent Road area of Cookstown on Thursday 6 July.
"NIAS despatched an emergency crew to the incident.
"Following assessment and initial treatment at the scene, the patient was taken to Antrim Area Hospital."
Police are appealing for information.
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