Pictures: Eight fire crews tackle Shrewsbury factory blaze

Police urged people to avoid the Lancaster Road area of the town and sealed off roads as smoke billowed from the Spel Products site in Harlescott.

Workers were evacuated and householders living nearby were told to keep their windows closed as there was possibility of fibreglass particles and chemicals in the air.

Eight engines from Shropshire Fire and Rescue Service were called to the scene.

The service's environmental protection unit attended the scene but only as a precautionary measure.

A spokesman for the fire service said: "There will be an investigation underway but the environmental protection unit wasn't actually needed. It was called out in case there was any risk to the environment but it was found that there was no risk."

He said the fire had been located in the winding room of the premises.

Eight crews from Shrewsbury. Albrighton, Baschurch, Prees, Tweedale, Wellington and Wem were on scene, as well as the incident command unit and safety officers.

Firefighters used four breathing apparatus, and four hose reel jets to tackle the blaze.

Officers from West Mercia Police, were also at the scene, diverting traffic while nearby roads were closed.

Police tweeted:

People took to Twitter as smoke poured over the area:

Phil Fairclough, 39, who was in the area at the time, said: "I saw the flames and wondered what was going on. There was lots of smoke and then the fire engines arrived.

"There was a horrible smell in the air."

David Griffiths, 48, said: "I was on my way home from work when I saw the smoke. I could smell chemicals in the air and wondered which building was on fire.

"People thought one of the factory chimneys had come down."

Work was being carried out to assess the damage.

Spel Products was unavailable for comment.

West Mercia police spokeswoman Holly Claydon-Bevan, a spokeswoman said: "We were called just prior to 2.50pm following a report of a fire at a premises on Lancaster Road.

"Members of the public are advised to keep the area clear to allow access for emergency services. Fire service also in attendance."

Spel Products provides products and systems for the storage, attenuation, monitoring, treatment and utilisation of surface water.

In February of this year the firm was ordered to pay almost £30,000 in fines and costs by Shrewsbury magistrates after an explosion in which a 45 gallon steel drum was blown apart.

Spel Products was told the blast could have killed or seriously injured workers.