A huge fire broke out at a scrapyard at Oakridge Lane, Aldenham in Watford this afternoon.
One local woman said she heard an “explosion” before the fire erupted.
Police were called to the scene at 2pm.
Thick black smoke was seen billowing above the flames, as fire services continue to tackle the blaze.
The smoke was spotted across Watford, Borehamwood, Bricket Wood, and Radlett.
Black plumes were observed from as far as London, Hertfordshire police said.
Roads in the area have been closed as a result of the blaze.
Smoke could be seen for miles.
One rail commuter told Express.co.uk: “I was on the train from London to Aylesbury and couldn’t believe how big the fire was.
“It is miles from the train line but we could clearly see the huge cloud of black smoke filling the air.
“It looks really serious. The ash cloud is so high planes are flying through it.”
Locals are urged to keep away from the area to avoid inhaling smoke fumes.
Hertfordshire Fire and Rescue service has warned residents close to Aldenham and Radlett to keep their windows and doors closed.
Herts Fire Control said on Twitter: “Further to our previous tweets regarding the SCRAPYARD FIRE in ALDENHAM – if you are in close proximity to the area of Aldenham and Radlett – please ensure your windows and doors are closed to avoid inhaling the smoke fumes.”
A police spokeswoman said: “Police were called by the fire service at 1.59pm to reports of a large fire in Aldenham.
“The road is currently closed and emergency services remain at the scene at this time.”
Herst police tweeted earlier: “Garston Fire and Borehamwood Fire were mobilised to reports of a scrap yard fire in Aldenham – before even booking in attendance this was quickly escalated to a MP6 with both Fire Watford appliances and St Albans fire and A07Fire joining due to the amount of smoke 1/3.”
This is a breaking story. More to follow…