METHANE gas burst into a 30m fireball at a piggery near Howlong yesterday.
Firefighters said the 2000-degree flash fire would have instantly killed anyone in its path.
The fireball swept over two large natural gas cylinders and officers feared the heat could turn them into gas-charged missiles.
Inspector Kernin Lambert, the duty commander for southern NSW fire brigade, said firefighters had also feared more explosions as methane gas continued to leak from an effluent pond.
Investigators now want to know how a cloud of gas first escaped the covered pond at the QAF piggery.
The pond at the Bungowannah property collects waste from pig sheds, with the methane a by-product of their storage.
Insp Lambert said nearby workers had escaped almost certain death.
“The tank contained about 20,000 cubic metres of methane, more than an Olympic pool, that’s huge,” he said.
“There was an enormous fireball.
“Witnesses said the fireball reached up to 30 metres into the sky.
“It burnt very quickly, we think for less than a minute.
“At least five people were in the area. They are very, very lucky.”
Riverlea chief executive Paul Pattison said contractors may have pierced the pond’s cover.
“We consider ourselves very fortunate — no one has been hurt, there is no impact on production and the stock unharmed,” he said.
“It is an accident that was all over in 30 seconds even though there was significant flame.”
Insp Lambert said firefighters had feared that the cylinders would explode, setting off more blasts.
“We faced the possibility of more major explosions,’’ he said.
“The production of methane continued after the first explosion and we feared there would be more explosions.
“The firemen kept those cylinders cool until they determined they were safe.
“We monitored the atmosphere and were able to mitigate against further explosions.”
“Fortunately, the staff at the site did all the right things.
“Their initial actions minimised the potential for further damage.
“They shut off the electrical systems early, shut off the gas and that removed the possibility any further ignitions.”
Three NSW Fire and Rescue tankers and seven from the Rural Fire Service attended.