The M25 has been closed in both directions between J22 (St Albans) and J21A after a large fire broke out at a commercial premises, with authorities warning of a risk of secondary explosions.
Fire at warehouse unit near St Albans
The fire has taken hold at a warehouse unit near St Albans, and the motorway has been shut as a precaution due to the risk of "secondary explosions, smoke and debris affecting the carriageway."
Hertfordshire Fire and Rescue Service are currently attending the incident, having closed the busy motorway. Ten fire engines were dispatched to the scene after the service was alerted at 9.21am.
Significant congestion and diversions
Significant congestion is being caused on the M25 and surrounding roads, including the A405 North Orbital Road and the M1 Southbound. National Highways has advised drivers to "allow extra time for their journeys and consider alternative routes" and has set up diversions for motorists.
In an earlier statement, the highways agency revealed that 15 fire appliances were battling the blaze and that the closure is expected to remain in place until emergency services deal with the fire.
Official statements
Deputy Chief Fire Officer Mark Barber stated: "We are currently responding to a fire at a large industrial unit in Ventura Park, Old Parkbury Lane, Colney Street, St Albans."
"Fire Control has received a significant number of calls regarding this incident, and I would like to reassure residents that firefighters are working hard to bring the situation under control. As a precaution, we are asking people living nearby to keep their doors and windows closed and to avoid the area while emergency services continue to deal with the incident."
"I would like to thank the public for their patience, understanding and cooperation. Please continue to follow our advice and avoid the area to allow emergency crews to work safely and effectively."
A National Highways spokesperson said: "M25 been temporarily closed from J21 to allow contractors to safely install full closure at J21a, once fully established it will be removed. Delays building currently 45 mins, 3 miles of congestion on the approach."
