CHEMICAL drums exploded and cyanide gas was given off during a fire at a scrapyard.
Clouds of smoke billowed across the Colne Valley from a tower of burning cars and chemical drums as firefighters tackled the blaze at J S Bamforth, of Milnsbridge, on Saturday afternoon.
Huddersfield Station Officer Dave Rawnsley said: "Forty-five-gallon metal drums were firing off and exploding in the sky.
"They were sealed containers and the lids were shooting off and coming down like giant frisbees.
"There was a lot of debris flying around."
Plastic and polyurethane from the burning cars gave off toxic fumes, including the cyanide gas.
Three teams of firefighters from Huddersfield, Slaithwaite and Brighouse were at the blaze on Colne Vale Road after they were called out at 2pm.
The fire is believed to have been started by children.
Site owner Steve Millas said there had been several fires at the yard in recent years.
He added: "We try to keep the kids out, but we are beside a footpath and cannot put barbed wire up. We keep mending the fence but they keep breaking it down."
Station Officer Rawnsley warned that youngsters were risking their lives by playing in the scrapyard.
"It is extremely hazardous, with battery acid, liquid petroleum, oxy-acetylene cylinders, iron filings and broken glass around.
"The cars are dangerous to play in as they are stacked up and unstable."
Mr Millas said there was no sign of any fire when he left the site at 12.45pm on Saturday.
But the fire was well-established by the time firefighters were called out, with at least 30 scrap cars on fire.
The vehicles were stacked seven-high, in a tower the height of a four-storey building.
Firefighters focused on salvaging a £250,000 crushing machine.
The equipment was then used to dismantle the burning tower, so firefighters could direct their water jet at the seat of the fire.
Water was pumped from the nearby canal.
Firefighters tackled the blaze without breathing apparatus, using an unmanned water jet, downwind of the blaze and other jets of water upwind.