The man, who was in his 40s, died at a property on Capgrave Crescent in Brislington in the early hours of Sunday.
The case has been referred to the Independent Police Complaints Commission as officers had previous contact with the dead man.
Two men held on suspicion of murder remain in custody. Two women who were arrested have been released on bail.
The victim had been seriously assaulted and had serious head injuries.
It is not known if he was alive when he was set on fire.
The dead man - who has not been named - had been questioned by officers on Friday on suspicion of breach of the peace.
He was released without charge later that evening and returned to his home in the Brislington area of the city.
Avon and Somerset Police have categorically denied claims in the community that the man had been arrested over alleged paedophile activity.
A man who died in Bristol was found by paramedics "in flames", police said.