Firefighters were tackling a huge blaze at a Bradford packaging factory today - more than 12 hours after it went up in flames.

Fire crews from across the county were called to the fire at Styrene Packaging and Insulations Limited, Low Moor, at 8.25pm yesterday.

One late-shift worker was initially unaccounted for but was later reported to have escaped unhurt.

Today crews were still trying to put out the fire, which had spread to the basement, after an exhausting night's work. At its peak more than 100 firefighters using three aerial jets and more than a dozen appliances, tackled the inferno which caused a massive plume of black smoke to billow 1000ft into the air.

People living nearby were warned to stay inside and keep windows shut but the acrid smoke, visible for miles, caused roads near the factory in Park House Road, to become clogged with traffic as people arrived to find out what was happening.

Police had to move drivers on to allow access for fire crews as the road to the Park House Industrial Estate became blocked.

West Yorkshire Fire Service Assistant Divisional Officer John Webster criticised their behaviour. "It was unbelievable - they made it very difficult for us getting into the fire as quickly as we'd have liked to," he said.

Sub Officer Mark Whitaker, of Bradford fire station, said: "At one stage police were having to pull spectators out of the gate. They were trying to get in. That's human nature for you.

"The heat from the fire was intense. The smoke was choking but the worst of it was being carried high into the air. It was the polysterene that was causing it.

"We were being showered by blackened polystyrene residue. It was hard work because of the combined heat of the fire and the weather. We had to keep drinking water."

During the night 80 firefighters in full heavy firefighting kit struggled against the thick choking black smoke and intense heat.

By 8am today the firefighting teams, who were replaced by reinforcements from Roth-well, Leeds and Huddersfield stations, were halved to about 40 firefighters as they still tried to put out the flames in the factory basement. The roof had collapsed and two of the walls were on the verge of falling.

Tony Thornton, of Park House Road, whose garden backs on to the plant, said: "We have had eight fires here in the last five years but this is the worst. I was just painting on the roof and my wife Edna heard a bang and shouted. It was one of the cylinders going up.

"There was suddenly smoke billowing up. Then we saw the flames which were about 40 feet high."

Philip Milner, of Wesley Avenue, saw the roof collapse. "After a few minutes, the roof caved in and a man who works there told us that the floor was a foot deep in polystyrene liquid," he said.

Employees at Styrene Packaging turned up at work today but were sent home until further notice. Its managing director Michael Edge is thought to be in Italy on a business trip. His brother Paul Edge, a director of the company, was at the scene this morning. He declined to comment on the fire.

Adjoining company LMS International Ltd, which produces drawers for the flatpack furniture industry, was slightly damaged.

Chief executive David Mends said: "The firefighters have done a sterling job to save the company and I'd like to thank them."

Other factories nearby were continuing to work normally today. Airedale Shutter Company director Steven Hill said: "All employees are at work as usual."

Fire investigators were expected to launch a probe into the cause of the blaze later today.