A man died in the Rochdale Canal on Dale Street in the early hours of Saturday morning.
Shortly after 4.30am police were called following reports two men were in the water.
Officers attended along with the Greater Manchester Fire and Rescue Service and two men were found.
Both were taken to hospital for treatment however a 26-year-old man died and the other, believed to be 34-years-old, remains in a critical condition.
Detective Inspector Debbie Oakes said: “At such an early stage of the investigation, we are not in a position to say with any certainty what has happened or why these two men were in the water.
“It would appear one man has gone into the water and the other has then gone into the canal to help but again I would stress we are at the very stages of our inquiries.”
Police are investigating the circumstances leading up to this incident and are appealing to anyone who has information about what happened to come forward and speak by calling 101.
For more on this story and many others, follow Mancunian Matters on Twitter and Facebook.
