More than 100 firefighters are battling a large blaze at an industrial unit in Essex following a “massive explosion”, authorities said.

Essex County Fire and Rescue Service said crews were called to farmland in Southend Road, between East Hanningfield and Rettendon, on Friday afternoon.

Locals said an explosion shook houses and sent a huge mushroom cloud towering into the sky.

East of England Ambulance Service said they were responding to a "significant incident".

Pictures show large plumes of dark smoke in the air which can be seen for several miles.

According to the fire service’s call logs, the fire was first reported at 4:50pm and is ongoing.

Steven Whan, 58, from Bicknacre, near Danbury, told the BBC he thought he had heard a jet's sonic boom when the explosion occurred.

"Our house shook, the doorbell went off. I thought it was a sonic boom because we've experienced that before," he says.

Whan adds: "The police have blocked off everything. You can't get nowhere near it."

Another local, David Harris, who lives about six miles away from the blaze, said: "It sounded as though somebody dropped a sort of pallet of bricks or something just over the road, it was that loud, it was incredible."

The emergency services have advised local residents to keep their windows and doors shut, while roads in the surrounding area have been shut by police.