Updated 9.45pm: The kitchen of a popular Auckland eatery has been gutted by a fire in central Auckland.

Hundreds of office workers were evacuated from Federal House and surrounding buildings in the city's casino precinct this afternoon.

Chef Al Brown has posted a photo to Facebook, saying the kitchen at the Federal Delicatessen has been completely burnt.

It's believed the fire started in the extraction hoods.

Al Brown says the damage at the neighbouring Depot Eatery is 'not too bad' by comparison.

He's pointed out the silver lining - nobody was hurt in the blaze.

Nearly 40 firefighters have been involved finding and fighting a fire in a building in Central Auckland.

Auckland Central Fire's Dave Woon says firefighters have entered the buildings to find the source.

He says the ducting is behind fascia, it's hidden, and they have to use thermal imaging cameras and pull away walls and things to find where the fire travelled.

SkyCity communications Colin Espiner says the affected building not only holds the popular Al Brown cafes, but houses a number of their corporate staff.

He says it's not clear when people will be able to return.

"We know there was a fire in the Fed Deli Kitchen, or in the extractor fan that leads off the kitchen. We don't know how it was caused or why, but it did create a lot of smoke which forced an evacuation."

Albert Street is closed as well.

Jonathan was at the scene and told Danny Watson what he's heard.

"I spoke to a fire warden earlier, it's a kitchen fire. But there was a lot of smoke coming out of a very small restaurant."