A witness has described hearing a 'boom' and 'echo' during a large explosion that killed four and injured another.
Police have declared a major incident after blast at a water recycling centre in Avonmouth.
Three of the people who died worked for Wessex Water, and the other was a contractor. The injured person's condition is not life-threatening.
It's been the confirmed the blast happened in a silo containing treated biosolids, and was not terror related.
Sean Nolan, who witnessed the aftermath of the explosion, said he had heard a boom but believed it to have been a vehicle collision.
“I heard what I thought may have been two trucks colliding by the way it shook the ground… it was big,” he told the PA news agency.
“I continued doing what I was doing, but a couple of the lads came out to see if I was alright.
Mr Nolan said there had been “a lot of commotion” in the minutes immediately after, but the incident itself had been “quite short-lived”.
“There were a lot of sirens coming in and some helicopter activity above as well,” he said.
“It (the helicopter) was circling for a good hour or so.
“It was quite short-lived, I’d say about two or three seconds. Sort of a boom and echo and then it just went quiet.
“That was it. There was no smoke, there was no after-effects of it.
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“I thought it must have been some sort of crash or some sort of impact or something like that.
“I was thinking I hope nobody is hurt… I just started to worry instantly about the condition of whoever was involved.”
Another eyewitness told BBC News: "We were inside the warehouse, the whole warehouse was shaking and we literally stood there in shock,”
