The body of Daniel Smith, 23, was discovered by firefighters under a railway bridge in Irwell Street at about 01:20 GMT on Wednesday.
Mr Smith, who was believed to have been sleeping rough for a number of years, had suffered multiple injuries.
Two men aged 24, from Manchester, remain in police custody for questioning.
Two men have been arrested on suspicion of murder after a man was found dead in a burning tent in Salford.