Six fire engines and the aerial ladder platform from Preston Circus have been sent to tackle a blaze above a restaurant in the centre of Brighton.
They have been at Iydea vegetarian, in Kensington Gardens, since about 5.30am, East Sussex Fire and Rescue Service said.
Drivers were warned to avoid the area and neighbours were advised to keep their doors and windows closed.
The fire service said: “East Sussex Fire and Rescue were called at 5.25am on (Tuesday) 24 September to reports of smoke at a commercial building in Kensington Gardens, Brighton.
“The aerial ladder platform, six pumps – two from Preston Circus, one each from Roedean, Hove, Newhaven and from West Sussex Lancing and Shoreham – are in attendance using two breathing apparatus, one hose reel jet and two main jets to put the fire out.
“The fire is believed to have started on the first floor of the two-storey building.
“The first floor and roof space have been affected.
“Please avoid the area as there will be severe disruption in the North Laine area this morning.
“Please keep windows and doors closed as a precaution.”