Two men aged 28 and 25 and a woman aged 20 were detained by detectives in Southampton.
The unidentified body was found by firefighters called to a blaze in the bin in Empress Road industrial estate in the city at around 3.10am on Sunday.
The arrested trio are from Southampton, a Hampshire police spokeswoman said.
Police are still appealing for information, particularly from anyone who may have witnessed suspicious activity in or around the industrial estate, off Thomas Lewis Way, overnight.
Detective Inspector Simon Baker, who is leading the murder hunt, said: "We are making urgent inquiries to identify the body."
The detective said he was unable to say whether the victim was male or female, their age or how badly burned the body was.
The area where the body was found is part of Southampton's red light district.