Around 80 firefighters are tackling a huge blaze in the centre of Hebden Bridge.
The incident started at La Perla restaurant, in Burlees House, shortly after 2am on Tuesday 2 August before spreading to adjoining offices.
Crews have managed to save nearby houses, but a number have been evacuated due to heavy smoke.
The town hall has opened its doors to all those affected by the incident.
Fire crews from across West Yorkshire are in attendance, with both Greater Manchesters and Lancashire Fire Services providing support.
Gas and electric engineers are at the scene and welfare units have been set up.
People living nearby are being asked to keep windows and doors shut. West Yorkshire Fire and Rescue Service say there is likely to be severe traffic disruption.
Calderdale Council has asked people to avoid the town centre. In a tweet, the council said: "Please avoid Hebden Bridge town centre area until further notice, there are several road closures due to a major fire. We have officers and wardens in the area."
Roads have been closed, including: Old Gate, Bridge Gate, Crown Street, Albert Street andHope Street.
Calder Valley MP Craig Whittaker wrote on social media: "Sad to see this iconic mill go up in flames during the night. Thankfully there are no known casualties.
"The town centre is currently closed off and people living in the town centre of Hebden Bridge are advised to keep windows and doors closed."