Detectives investigating a 'completely reckless' arson attack on a mill have released CCTV footage of four suspects.
The footage captures one man carrying what appears to be a crowbar - and another running with two green cans.
A gym owned by former world boxing champion Anthony Crolla was one of several businesses destroyed in the resulting blaze at Morton Mill in Failsworth, Oldham.
The men, all dressed in black with their faces covered and gloves on, are captured running around the building and trying doors in the early hours of March 29.
Police said six businesses in total operated from the 106-year-old mill.
It's thought a number of gyms, a furniture store and a sign writing firm were based there.
All have been unable to open since the fire, police said.
Detectives said the fire 'could easily have had devastating consequences' but thankfully no-one was injured.
At the height of the blaze more than 40 firefighters were on the scene.
Pictures and video show flames shooting above the rooftops of surrounding buildings.
Police said they were called to the scene by the fire service at 5.30am.
Fire crews remained at the scene for days, making sure the blaze was fully extinguished and ensuring the building was structurally safe.
In a statement, GMP said: "Unfortunately, the fire was too severe to prevent major damage.
"Six businesses operate their services from the mill and have been unable to open since the fire.
"Following enquiries, detectives have established that the fire was started deliberately and have released CCTV footage from that morning as part of an appeal for information."
Detective Constable Steven Gilliland said: "This fire has affected a lot of people from business owners to the local community and whilst a month has passed, we're working hard to trace those responsible but we need the public's help.
"It goes without saying that this incident could easily have had devastating consequences but thankfully no-one was injured by the blaze that nine fire engines had to be deployed to tackle.
"This can only be described as a completely reckless crime and I would urge anyone with any information, no matter how small or insignificant it might seem, to get in contact with police."
One of the gyms involved was Fox Amateur Boxing Club, where Crolla honed his talents as a youngster.
The former WBA lightweight world champion, who now owns the club, told the Manchester Evening News: "It's heart-breaking to be honest.
"I can't get my head round it.
"I've got lots of great memories from there. I trained there as a kid, I trained there as a pro.
"But it's not just about me. It's about the kids in the club. It's about my friends who have other businesses in there.
"It's their whole livelihood.
"They've put so many hours in, they've put their hearts and souls into building up their businesses."
Anyone with information should call police on 0161 856 8999 or 101 quoting incident number 300 of 29/03/2020, or Crimestoppers on 0800 555 111.
