A massive blaze which destroyed part of an historic former textile mill is being treated as suspicious, investigators have revealed.

About 100 firefighters worked through the night to quell flames pouring from the empty Grade-II listed building at Dalton Mills, in Dalton Lane, Keighley.

Crews from across West Yorkshire were scrambled to the 142-year-old landmark building at about 6.50pm on New Year’s Day.

Speaking from the scene yesterday, Chris Clarke, a fire investigation officer, said West Yorkshire Fire Service were scouring CCTV as part of a joint investigation with police.

“We are treating it as suspicious,” he said. “There is evidence to suggest that there may have been people in there who should not have been.

“We are working with police to establish what has happened prior to the fire.”

Detectives from Airedale and North Bradford CID have also been assigned to the investigation, a police spokesman said.

At its peak, the huge blaze caused the roof over the central section of the historic building to collapse. Fifteen fire engines, aerial platforms and a specialist command unit were joined by ambulances in Dalton Lane as the fire raged.

Police cordoned off the mill, which has been used in TV and films, and blocked both ends of Dalton Lane for more than three hours.

Firefighters were on standby through the night after a gas main inside caught fire.

Eye witness Asghar Hussain, 52, of Frederick Street, said: “I saw the flames coming from the middle part of the building.

“They were coming up through the roof and then it collapsed and the whole section of the building was on fire.

“It is lucky that the Burgess Ford garage didn’t go down with it but the firefighters did a good job to contain it.

“The way the flames were going, I thought the whole building would burn down.”

He added: “It is a landmark building and I think it has been sold because it was up for auction two or three weeks ago.”

A spokesman for Burgess Ford said they had to move their vehicles at the height of the blaze and some had been damaged.

The partially restored mill is a major part of the Airedale Masterplan, the regeneration blueprint for the Aire Valley region.

Part of it has been turned into office space following a multi-million pound conversion.

It had a starring role as Marlborough Mills in the BBC adaptation of North and South, as the set of BBC 1 show Sunday Life, in numerous Bollywood films, and most recently as a backdrop for Bedlam, a forthcoming drama series featuring Will Young.

Bradford Councillor Khadim Hussain (Lab, Keighley Central) said he had been shocked to hear about the major blaze.

He said: “For a long time, we have been very much committed to Dalton Mills as an area for regeneration. It is a setback that I hope can be overcome.”

Magna Holdings Ltd, the mill’s holding company, were unavailable for comment yesterday.