A massive fire erupted in a landmark power station, filling the sky with thick smoke and flames.
Some 15 fire crews spent several hours tackling the blaze, which broke out at the coal-fired Ferrybridge C Power Station just before 2pm today.
All workers inside the plant, which is run by energy giant SSE and stands next to the River Aire in West Yorkshire, were quickly evacuated and no one was injured in the blaze.
The area was cordoned off by fire crews and specialist hazard response teams from West Yorkshire's Ambulance Service.
Pictures show children watching as fire crews doused water over the blaze, which tore through the third floor of a four-storey building and was eventually brought under control in the early evening.
SSE, one of Britain's 'Big Six' energy firms, said the fire triggered their "emergency response procedures" and that the safety of their staff and customers was their top priority.
And the National Grid confirmed the fire had no impact on electricity supply as the plant was on summer shut down.
A spokeswoman said: "They were not generating onto the grid so it is not going to affect our operations at all."
West Yorkshire Police warned drivers on the nearby M62 and A1 to be cautious in light of the billowing smoke.
Inspector Helen Brear said: "Strangland Lane, Knottingley, is closed but at the moment neither the M62 or A1 are.
"Motorists are, however, advised to exercise caution on these roads and we will be continually monitoring the situation to see if any other roads need to be shut."
The power station has been in operation since 1966, and according to SSE's website, has two 198m (650ft) high chimneys and eight 115m (380ft) high cooling towers, which are the largest of their kind in Europe.
The site has undergone major changes recently in the light of the EU's Industrial Emissions Directive, which aims to reduce pollution, and a 65MW multi-fuel plant was expected to start generating power next year.
SSE said they will launch a full investigation into what sparked the blaze, and that they hope to send specialists into the plant tomorrow morning once the station had cooled to begin their probe.
The fire service said a structural engineer had been "notified" about the incident.
In a statement released this evening SSE said: "All persons on site have been accounted for and there are no reported injuries.
"The company's practised emergency response procedures were immediately activated and we are currently in the process of ensuring the site is made secure and safe.
"The affected area in the site vicinity has been isolated by police and the West Yorkshire Ambulance Service hazardous area response team are also present. West Yorkshire Fire and Rescue Service remains in attendance and is dealing with the incident with support from SSE engineers.
"West Yorkshire Fire and Rescue Service has indicated the fire is now being brought under control. Due to planned maintenance neither of the affected units had been operational over the summer and therefore had not been supplying power to the National Grid at the time of today's incident.
"SSE will be undertaking an investigation to establish the full extent of damage in due course. Early indications show the fire itself started in unit 4 but also had some impact on Unit 3.
"Currently we do not expect Unit 4 to return to service in this financial year. Unit 3 is not expected to return to service before 1 November. Our immediate priority is to manage the incident and to ensure the safety of staff, contractors and the general public."
Ian Bitcon, area manager of the West Yorkshire fire brigade, said the fire had been ferocious and at its peak sent flames 100ft into the air.
Crews are expected to work through the night dampening down the blaze, which has caused part of the plant to buckle because of the searing heat and damage.
He said: "We are at the dampening down stage, so the flames are mainly out but it is not entirely extinguished. We expect there to be crews here right through the night.
"Obviously it is very difficult to fight a fire that is about 100ft in the air. Fires at that height can be quite unpredictable.
"We are very happy we managed to stop the fire from spreading to other buildings around it. At various stages it didn't look like we would do, but we fought hard.
"There has been a partial collapse of the building. The building has buckled and is around 30ft lower than its sister building because of the fire."
He said it might be a few days before the building can cool off and be safe enough to send investigators in.
He said: "It is a big structure and it has become very unstable because of the fire.
"The company will need to demolish the part of the building affected by the fire, but we are still at the stage where there is enough firefighting that is going on that they cannot start that yet.
"They will probably make an assessment on that tomorrow morning and carry it out over the next few days."