More than 70 firefighters battled a major blaze after chemicals exploded at an industrial site in Ayrshire.
The fire at the former ICI factory in Stevenston near Irvine, has been brought under control but residents have been urged to stay indoors.
A 1km cordon has been put up around 200 houses, police said. There are no reports of injuries.
Eyewitnesses told the BBC that flames reached 100ft into the air and could be seen from 10 miles away.
Around 40 firefighters remain at the scene, but the authorities say there is no significant risk to public health from the incident.
James Smith, 54, who lives about half-a-mile from the blaze, described how he heard explosions and saw huge flames as the factory went up at about 2030 BST.
He said: "It was enormous. The flames were a couple of hundred feet high. It was like a white flame.
"There were a couple of explosions, like gas canisters."
John Wallace, 45, who lives 1km away from the Lundholm Road factory, was first alerted to the fire when a bright light drenched his living room.
The scene outside Mr Wallace's house
"We thought it was a fire engine at first but I looked outside and saw these large flames leaping over the houses," he said.
"I probably heard about four or five explosions. My wife went and fetched her mother who lives in that direction as the heat and flames were very worrying."
He added that the flames seemed to die down after 45 minutes and that it was not the first time a fire had broke out at the factory.
"My wife's uncle, who was a fireman, died after being seriously injured in a explosion there," he added. "This plant produced a lot of explosives for the war."
Frank Chan was walking back to his bed and breakfast in nearby Ardeer when he heard the explosion.
"It was just after 8pm as I'd been shopping at Morrisons and I was the last to leave the shop," he said.
"As I walked along I heard the explosion and saw the flames."
Officers said that the chemical explosion involved flammable nitro-cellulose.
Strathclyde Police added that the factory is now owned by a firm called Nobel Enterprises.
The company specialises in nitro-cellulose, and its website says it produces the chemical for the inks and coatings market.