A series of explosions have rocked Derby city centre resulting in a huge plume of black smoke rising over the city.
Dramatic photos capture the smog bellow from a factory after a fire.
Residents in Derby say they heard at least three explosions in one hour.
"I live nearby and I have heard two explosions very loud in the last hour.
"A large cloud of black smoke is now spreading over my garden and a stench of burning is getting stronger," one resident told Mirror Online.
It is understood the fire, described as a "serious incident", happened at a factory on an industrial estate. Authorities have warned residents to remain indoors.
Train services have been delayed and trunk roads are shut.
People on Twitter described the horror at the ground "shaking".
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"Crowds are gathering to see the plumes of smoke which are visible for miles around," wrote one person online.
Robbie Bunting, 24, was at work at a nearby business when he heard a huge bang.
"I was just sitting at my desk, and all of a sudden there was a huge bang, everyone was walking around in the corridor and we went to look outside to see what it was, and there was a huge fire billowing black smoke over us.
"And then there were several more explosions. So we all ran back in, grabbed our stuff and left," he said.
Nearby buildings, including a police station, have been evacuated.
A Derbyshire Police spokesman said: "St Mary’s Wharf police station in Prime Park Way, Derby has been evacuated due to a large fire at a business premises on Chester Green which has resulted in a series of explosions.
"We are aware and dealing with a series of explosions in Derby. We are advising residents to stay indoors and keep windows shut at this time due to the smoke.
"An investigation is under way as to the cause of the fire, but it is not thought to be suspicious at this time."
One woman was walking in a park around two miles away when the blasts happened.
He said he heard three big explosions and further quieter ones.
A spokesperson for East Midlands Trains said: "There is a fire next to the track north of Derby Station.
"Services on our London St Pancras/Derby/Sheffield and Matlock/Derby/Nottingham routes are currently disrupted. More information to follow."
A spokesman for Derbyshire Fire and Rescue Service said: "We are currently dealing with a commercial building fire in Derby City on Enterprise Way. People are urged to keep windows and doors closed due to the smoke in the area. No further information at present."
The fire is believed to have happened north of Derby station. There is a large industrial unit - West Meadows - in the area.
Derby County are at home today to QPR in the EFL Championship.
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The game is unaffected as yet.
But Pride Park is a short walk from the train station.
It is unclear if there are any injuries at this stage.
Emergency services are at the scene.
The first loud bang was heard at around 1.40pm.
