An investigation into the cause of the fire is underway.
Detective Superintendent Phil Owen said: “We are working with our colleagues from the fire service to establish how this fire, which has tragically claimed the life of a firefighter, started.
“We have already arrested two juveniles in connection with the fire and our enquiries are continuing.”
Greater Manchester Fire and Rescue Service said Firefighter Stephen Hunt, 38, from Philips Park Fire Station in Manchester, lost his life.
He was part of the team responding to a blaze in Paul’s Hair World in Oldham Street.
It had been a particularly difficult incident due to the complex layout of the building and the amount of materials inside.
He got into difficulty inside the building at around 8.35pm, along with another frefighter and both were pulled out by their colleagues and treated by the Ambulance Service before being taken to hospital.
Firefighter Hunt died and his colleague remains in hospital but his injuries are not thought to be life threatening.
County Fire Officer Steve McGuirk said: “We are devastated by the loss of one of our colleagues who has died in the line of duty.
“We never expect to lose a colleague in this way and it brings home the dangers that our firefighters put themselves in every day to keep the community safe.
“Stephen had been a dedicated firefighter since 2008 and we are all in a state of shock.
“It is a very sad day for Greater Manchester Fire and Rescue Service and all our thoughts are with Stephen’s family and friends.
“Details of exactly what happened are unclear at this stage but will be investigated thoroughly and independently. We have asked our neighbouring Fire and Rescue Services to immediately start an investigation into the incident and circumstances leading to this terrible tragedy.
“We are working alongside Greater Manchester Police to establish the cause of the fire. At this stage arson is not being ruled out.”
This morning crews were still on the scene.
“They are clearly devastated by the loss of their colleague and I pay tribute to their professionalism, courage and dedication - while in mourning they are continuing to keep the community safe,” said officer McGuirk..
“I would also like to thank the Ambulance Service’s team who battled to save Stephen.”
A Facebook page has been set up for the public to express their sympathies at www.facebook.com/manchesterfire