DINERS have told of the dramatic moment they fled a Southampton fast food restaurant when a blaze broke out in the building.

Families rushed out of the Burger King Bargate Street branch in the city centre leaving half eaten chips and burgers strewn on tabletops as smoke poured from the roof.

Today an investigation has been launched into what caused the blaze - which occurred at the height of the lunch-time rush.

Last night bosses had began assessing the damage and were unable were unable to confirm when the restaurant would re-open.

But staff there told the Echo eight colleagues and around 25 diners there had escaped unharmed.

The fire broke out shortly before 12.12pm in ventilation ducts on the first floor area housing staff changing rooms and lockers.

Customer Nikki Long, 26, from Marchwood, was queuing for lunch when the drama unfolded.

She said: "Somebody came running in and said 'there's a fire on the roof!'.

"They were panicking. The workers realised there was a fire and evacuated everyone. They did a really good job of keeping everyone calm. The fire service were there in an instant."

Her friend Aaron Down, 26, from Hythe, said: "People had to leave their food on the table. People tried to grab what they could of it. The smoke was quite thick at one point."

Lauren Barker, 16, from Millbrook, was waiting for staff to prepare her order and said: "We were getting an ice cream and then we just heard someone say there was a fire and we had to get out."

Bystander James Marley,35, from Eastleigh, was on his way to the barbers in High Street at the time and said: "I saw lots of smoke and the whole area stunk of really obnoxious smelly smoke. I just thought it was something on the air.

"When I came out the barbers 30 minutes later there were firefighters everywhere."

Josh Newland, 20, from Millbrook, saw "billowing smoke" and said: ""At first I thought it was a bin fire and but then I saw it was Burger King.

"I saw some flames at the top of it."

More than 35 firefighters and five engines from St Mary's, Redbridge, Totton and Romsey arrived to tackle the blaze - using an Aerial Ladder Platform (ALP) to rise above the building.

Crowds stood watching open mouthed and police closed the road as crews wearing breathing apparatus used hose reels to tackle the flames.

They climbed onto the roof to put out flames which had spread from the shafts to cavity walls.

They also cut away roof timbers and timber boards to help dampen down the building.

Officer in charge Mark Budden from St Mary's said the nature of the ducts made it "difficult" to gain access but said damage was restricted to the staff areas rather than the main part of the two-floor restaurant - which suffered minor water damage.

He suspected the cause was down to a fault with an extractor fan but that investigations are still ongoing and added: "Thanks to the swift action of Burger King staff in evacuating the building all customers and staff are safe and accounted for."

Restaurant staff did exactly what they were trained to do evacuation the premises and customers."

Some customers who kept their receipts were able to obtain replacement food or refunds from neighbouring Burger King restaurant in Above Bar.

The Echo contacted Burger King but no-one was available for comment last night.