Five people have been arrested over a suspected arson attack which gutted a mill used to film scenes for Peaky Blinders and Downton Abbey.
A huge blaze engulfed the historic Dalton Mills complex in Keighley, West Yorkshire, on Thursday.
No-one was inside the building, in Dalton Lane, at the time of the fire and no injuries were reported.
West Yorkshire Police said the five suspects were being questioned on suspicion of arson.
At the height of the blaze, which started at about midday, 120 firefighters were at the scene and one eyewitness said he watched the inferno take hold "within minutes".
Bradford District Commander, Benjy Bush, said: "It was a really ferocious, challenging fire, we had 20 fire engines and two aerial appliances here, the police and ambulance were on the scene, as well as utilities and Bradford Council.
"We won't be putting firefighters inside the building as it is structurally unsafe.
"Possibly the building could be saved, but that's down to the structural engineers."
Two fire crews remained for damping down on Friday morning, with about 10 firefighters continuing to throw water on the site to prevent the fire from re-igniting.
Ben Oakley, from Save Britain's Heritage, said there may still be a chance to preserve the building, and his organisation had been "involved in saving a lot of enormous and fantastic industrial landmark mills across the north and in Yorkshire.
"These buildings have stood empty and are deteriorating - many of them for a very long time - and whilst the impressions can look terrible and be very disheartening, perhaps a lot more can be done than meets the eye."
The mill had been used for a number of film and television productions in recent years.
Richard Knight, from Screen Yorkshire, described it as "a destination in its own right".
Built in 1869, it was once the largest textile mill in Yorkshire, employing more than 2,000 workers.
It was struck by a serious fire in 2011, when it was believed copper thieves set fire to the site as they tried to burn off insulation to steal metal.
The complex fell into disrepair before being partially restored and taken off English Heritage's at-risk register in 2015.
West Yorkshire Fire and Rescue Service said a multi-agency inquiry was due to start later.
Police are appealing to anyone who may have seen anything suspicious in the area between 11:30 GMT and midday to contact them.
Officers are also looking for drivers who may have dashcam footage from the scene to come forward.