EYEWITNESSES described seeing huge balls of black and green smoke as firefighters battled a blaze caused by arsonists.

The flames destroyed a caravan and an allotment building on land near to a primary school in Farnworth.

There were also loud bangs as gas canisters exploded.

Smoke, coming from the site just off Devon Street, blew on to the A666 St Peter’s Way, slowing down traffic on the dual carriageway.

Anthony Marsh, aged 27, said he had often seen an elderly man tending to his garden in the allotment, and at the time he was worried the man might have been in there.

He said: “It scared us all. There were big, massive greeny-black clouds of smoke and balls of flames.

“We really hoped no one was inside, because you do hear about things like that happening.

“It was spreading really quickly and smoke was going on to the railway, it was really scary.

“There was a massive bang because one of the gas canisters exploded.

“I warned the fire brigade before they went in that it could be really dangerous. I have never seen anything like it.

Two fire engines and police were called to the fire, which was started deliberately in either the wooden structure or the caravan and affected both.

No one was injured and All Saints C of E Primary School was not affected.

The incident happened on Saturday and the fire was raging for two hours from 10am to noon, when firefighters finally managed to put it out.

Mr Marsh and his family live in Burnham Walk, over the train tracks from where the fire happened.

His younger brother Craig, aged 19, was the one who called 999.

He said: “It’s so near the school too, so it was really worrying.

“The fire brigade did a great job though, they were in there straight away, no messing around.”

Greater Manchester Fire and Rescue Service confirmed it was called to the incident shortly before 10am on Saturday, and that it was being dealt with by police as an arson attack.

Arson is the largest single cause of major fires in Greater Manchester.

A GMFRS spokesman said: “Arson costs millions of pounds each year, it also ties up fire service resources, putting lives at risk. Anyone caught will face prosecution and a criminal record.”

Any one with any information should call police on 101.