Emergency services were called to West Meadows in Ipswich at around 10.10pm on Sunday to reports that “a number of properties” were being damaged and two caravans had been torched.
The fires have since been contained and there were no reports of injuries, although the police said fire service and ambulance teams remained at the site.
Four men and one teenage boy were arrested on suspicion of violent disorder during the incident.
A 23 year-old man from Barnsley, two men aged 31 and 22 from Ipswich, a 19 year-old man from Wickford, Essex, and a teenage boy were taken into custody for questioning.
A 20-year-old man from Wickford, Essex was also arrested on suspicion of causing criminal damage.
One of the men suffered injuries from a dog bite as they were arrested and was taken to hospital.
A horse that was injured in the incident died at the scene.
Suffolk Police said in a statement: “Police were called at around 10.10pm last night, Sunday 11 December to reports that a number of properties were being damaged and that two caravans had been set alight.
“The fire service have contained the fires and are continuing to maintain a presence. It is not believed that anybody has been injured at this stage.
“Officers are working closely with partners in the ambulance, fire service and local authority. The situation is being carefully monitored.”
Two men, aged 18 and 32, are believed to have died after they were stabbed at the site near the A14 on Thursday.