Around 300 tonnes of electrical equipment waiting to be recycled has been destroyed by a massive fire in Sittingbourne, it has been revealed today.

Fire chiefs confirmed around a third of the depot, in Gas Road, Milton Regis, has been badly damaged in the blaze that broke out yesterday morning.

Dozens of firefighters have been fighting to tackle the inferno, which left two men in hospital, at Sweeep Kuusakoski since about 8.10am yesterday.

Crews continued to work overnight, spraying water onto the blaze from above as they raked over the area and damped down hotspots.

As smoke still billowed from the site today, people living nearby were warned to keep their windows and doors shut.

Kent Fire and Rescue Service said the operation was being scaled down to around 20 firefighters this morning - and will be further reduced this afternoon.

Incident commander Jim Ramsden told KentOnline the fire was under control - but not extinguished - this morning. Control of the site was handed back to Sweeep by 3.30pm.

Speaking from the scene, Mr Ramsden said: "We have scaled down operations to four pumping appliances and we will remain in attendance throughout the day, assisting the site management team to bring the site back to normality and to monitor the effects of our fire-fighting operations in relation to the environment and the local community."

An investigation has been launched by fire chiefs and company bosses into the cause of the blaze, which is not being treated as suspicious.

The firm today said the fire was contained to one corner of the building and it is continuing to accept deliveries of waste electronic equipment.

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Mr Ramsden added: "At this stage we haven’t got significant detail on how the fire started and exactly where, but our fire investigation team will be visiting the site to make preliminary investigations and get to the cause of the fire.

"We're not intending to involve the police in any further investigations in relation to the cause."

The brigade said it is working closely with the Environment Agency and the local authority to monitor levels of smoke still entering the atmosphere - and urged people to report ill health from fumes.

The Environment Agency said officers were today monitoring water quality in Swale amid fears it might have been affected by the fire-fighting.

They are working to protect a nearby creek, of scientific interest, from contamination.

Two men - believed to be in their 20s and workers at the depot - were yesterday treated at the scene for breathing in smoke before being taken to hospital by ambulance.

Last night, crews used cold-cutting equipment to break up smouldering material before moving it with diggers to help access the blaze.

Sweeep Kuusakoski claims to be one of Britain's leading waste electrical and electronic equipment collection and recycling specialists. It was set up in 2007 and now employs 150 people.

A spokesman said: "Our emergency evacuation procedure was activated and emergency services notified.

"Two people have been taken to hospital with minor injuries and are awaiting treatment.

"The fire was restricted to the waste electronics delivery area of the site and is now under control.

"We are initiating a full enquiry and working with the relevant agencies into the cause of the incident."

Video: Plumes of thick smoke billow from the recycling centre fire

Clear blue skies were turned black as smoke began pouring from the blazing £5million plant, which is said to be one of the most "environmentally robust" recycling centres in Europe, yesterday morning.

Up to 60 firefighters began directing water jets at the blazing building, whose blackened roof had partly collapsed.

By 1pm, the number of firefighers at the scene had been scaled down to around 35 and the blaze was being tackled with compressed air foam.

As the huge fire-fighting operation continued, a passer-by said the flames kept flaring up just as they appeared to be dying down.

Kent Fire and Rescue Service said 10 crews were sent to the scene at 8.10am.

It had advised local people to keep their windows and doors shut as a precaution while smoke continued to billow from the building.

A large exclusion zone was set up around the scene of the blaze while the huge fire-fighting operation continued.

Speaking at about 10.30am, KentOnline photographer Andy Payton said: "There is a huge plume of black smoke that has been rising over Sittingbourne.

"There are extensive flames and the building looks like it's been quite badly damaged.

"It's beginning to look under control. The smoke has changed colour and turned grey, so I suspect the firefighters have been able to start to bring it under control.

"It is a slightly awkward site to get to - it's one of the older industrial parts of Sittingbourne and access is very limited, but they have got a lot of hydrants in the area."

A policewoman directing diversions said the roads around the depot were expected to stay shut for most of the day.

The scale of the fire sparked fears the nearby Mill Way trading estate might have to be evacuated.

However, Gill Epps, staff member at Dunelms on the trading estate, said it was business as usual.

She said she first became aware of the fire when she saw smoke billowing above rooftops near her home in Cryalls Lane, Sittingbourne.

"We can see lots of smoke from the store kitchen," she said. "But no flames. The fire's quite a way from the back of the store. But there is soot settling on cars parked on the trading estate."

Fire crews at the scene of the blaze. Video: Andy Gray

Last November, Sweeep achieved a world first with the development of a ground-breaking furnace - becoming the first centre to be able recover lead and glass from old televisions and computer screens on a commercial scale.

It injected £2million into the pioneering technology to recover lead and pure glass from leaded cathode ray tubes (CRT).

The new plant recovers one kilogramme of lead from each of the 4,000 CRTs it can process a day by heating the granulated leaded glass to 1,000C.

In May 2011, the firm was named Recycling Business of the Year at the letsrecycle.com Awards for Excellence in Recycling and Waste Management - seen as the "Oscars" of the waste industry.

At the time, Sweeep said it had invested more than £6.5million and processed 10 tonnes of waste electrical equipment every hour. It also recycles 4,000 televisions and monitors a day and is powered by 100% renewable energy.

The firm says its Finnish sister company is one of the largest suppliers and refiners of recycled metals in the world.

For full coverage of the fire, pick up a copy of the Sittingbourne News Extra - out on Wednesday.