Crews were called to Ventura Park in Colney Street, St Albans, at 9.21am. Deputy Chief Fire Officer Mark Barber said: "We are currently responding to a fire at a large industrial unit in Ventura Park, Old Parkbury Lane, Colney Street, St Albans. "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. "Please continue to follow our advice and avoid the area to allow emergency crews to work safely and effectively." Crews are continuing to bring the blaze under control but it is expected to take several more hours to fully extinguish.