A Barnsley man and teenage boy were arrested over a disturbance at a travellers' site.
They were arrested over an incident the West Meadows travellers' site in Ipswich, in which two caravans were torched and a horse was killed.
The Barnsley due were arrested along with two men aged 31 and 22 from Ipswich and a 19-year-old man from Wickford, Essex.
They were held on suspicion of violent disorder.
The incident came the night before a 17-year-old, who cannot be named for legal reasons, was charged with the murders of Barry Street, 32 and 18-year-old Nathan Oakley, who were stabbed at the West Meadows travellers' site last Thursday.