Two firefighters were killed in a blaze at a fireworks factory in southern England on Sunday which sent explosions high into the sky for hours and created a plume of smoke visible for miles, police said Sunday.

The fire began at the factory near Lewes, about 60 miles south of London, around 2 p.m. Sunday afternoon, Sussex Police spokeswoman Sue Heard said. Police said they had launched an investigation into the cause of the fire.

About an hour after emergency crews, including dozens of firefighters, arrived on scene, there was a large explosion, officials said.

The two members of the East Sussex Fire and Rescue service who died were a 49-year-old firefighter and a 63-year-old member of the support team, department spokesman Gary Walsh said.

The 63-year-old killed was a retired firefighter who had returned to work in a support role, Walsh said.

Another dozen people — two members of the public, nine from the fire service and a police sergeant — were taken to local hospitals for treatment, officials said. Two of the injured were described as being in serious condition.

The factory was located in the middle of a relatively rural area, Jason Winter, whose family owned the factory, told Sky News. He said he had no idea what had sparked the fire.

"It could be anything. It's too early to say at the moment," he said. "Obviously, there's no smoking or anything so there's nothing like that (which) could start it.

"These fireworks have to be stored somewhere. They're in a rural area, they're in containers, they're properly stored."

East Sussex police Assistant Chief Constable Jeremy Paine said it was a massive blaze, and that officials had decided to let it "burn for a while." A cordon of 220 yards had been set up around the fire, Paine said.

Witnesses said they heard the enormous explosions about an hour after emergency services raced toward the fire.

"We knew it was a fireworks factory," said 30-year-old Richard Mitchell, who watched from outside the nearby The Anchor Inn pub.

"It was like a fireworks display with a fire in the middle of it. It was manic. It went on for about half an hour before dying down a bit. We saw 10 or 12 fire engines go past as well as four of five ambulances. It was obviously a major incident."