Brighton's largest shopping centre lost business from more than 15,000 customers' yesterday as the entire building and the surrounding area was evacuated after an explosion.

Churchill Square shopping centre was evacuated and a blanket cordon thrown around it after the blast caused by a gas canister in an empty unit at about 8.20am.

Nearly 1,000 staff members were thought to have been evacuated and closures to West Street, Western Road and surrounding roads caused travel disruption around the city.

The building reopened at around 2pm after almost five hours.

Pat Matthews, from building firm Ecobuild, was working in the empty unit when the explosion took place.

He said: "We were about 10ft away from it when it happened.

"It looks like the regulator on the gas bottle has gone and it just started shooting out flames.”

Mr Matthews, who was working on the unit between the Vision Express and Apple stores with about 15 workers, told how they heard the bang.

He added: "It was loud enough for us to run away, put it that way.

"The flames were about 5ft high and there was a load of black smoke coming from it so I rang the fire service.

"There haven't been any injuries as far as I know, but a few guys were still in there when we left so I don't know about them."

Wayne Thornton from East Sussex Construction, who was also working at Churchill Square at the time, said: "If those things [gas bottles] explode, the shrapnel can fly up to 500m, so it's lucky there was nobody in there because they'd be gone."

An East Sussex Fire and Rescue Service spokeswoman confirmed it was an acetylene cylinder that had caught alight in a storage area where some building work was being carried out in the empty unit soon to be Pull and Bear.

Anna Kubicka, assistant manager of Costa on Kings Road, said: “I was in work at about 8.15am and heard the alarms go off.

“The next thing I knew the building was being evacuated, so we were out.

“I got a call from the branch up at Western Road and because it was busy, so I came up here as soon as I could to help out.”

One employee from a Churchill Square shop said: “The fire alarms didn't go off but somebody was banging on the windows saying get out, get out.

“We just dropped everything and got out of there.

“We thought because there were no alarms that it was a bomb scare.”

Unexpectedly, The Grand hotel in Kings Road became an evacuee hub as general manager Andrew Mosley put people up in his conference suites after hearing there was a problem.

He said: “A local company who use us anyway asked if they could come down so about 350 of their staff were put in our main suite.

“And then a little bit unannounced, which didn't matter because we're good at that sort of thing, about 400 or 500 staff covering every shop in Churchill Square arrived.

“Strangely, it was a quiet day for us in terms of conferences, so we've put people up in those facilities and where it's been required we've provided coffee and sandwiches.

“A lot of the people, judging by comments, haven't been to The Grand before so they're commenting on how lovely it is so we've given them a voucher for discount on spa treatments and hopefully we'll see them again soon.”

The local company, Friends Investment based on West Street, packed out the main suite and staff were in good humour with some even hinting at a game of hide and seek.

Meanwhile, staff from Churchill Square stores were scattered out across The Grand, with many choosing to soak up the glorious autumnal sunshine.

One such staff member, Teresa Foster from The Entertainer, said: “I was due in at 9.30am and I saw all the commotion so I knew there was something going on.

“We have all been sat out here since about 11am soaking up the sun because there's not much room in The Grand.

“I went and had a little sleep on the sofa in the hotel, which was very nice.

“It's been quite a nice day all in all but we'll have to make up for the lost time and hit targets when we get back in.”

Sheena Hewens, who works at Clinton Cards with Lisa Phillips, said: “It wasn't until I saw the fire engines that I realised something was going on.

“And with us being a card shop we were pretty worries about our stock, but thankfully it's all ok.”

Ryan Grimond, manager of HMV's Churchill Square branch, said: “I got into work and was reading reports and setting targets for the day and suddenly the alarm went off.

“Initially I thought it was a drill, but there was panic in the Churchill Square staff's eyes so we knew something was up.

“We got outside to see police cars, fire engines and an ambulance and we were told there had been a gas explosion.”

At about 1pm, staff were slowly being let back in as the cordon is lifted and buses were also returning to normal.

By 2pm, the shopping centre had reopened to the public, some of which had been waiting all day to splash out at the popular mall.

Sam Bridley and Karen Forrest had set yesterday aside to get some early Christmas shopping done and had been waiting to get into the centre since 9.30am.

Ms Bridley said: “It's very frustrating because absolutely everything we need is in Churchill Square so we've not been able to get anything done.”

Ms Forrest added: “We'll hopefully have 30 or 40 minutes to cram some in now before the school run, but it looks like we'll have to make other plans to come back.”