An investigation has been launched into two explosions at Exxonmobil’s Mossmorran plant in Fife.
It is understood the blasts happened on two separate occasions on 2 and 12 August.
BBC Scotland understands the first boiler exploded at about 07:00 and had a blast radius of 20-25 metres.
A Health and Safety Executive (HSE) spokesman said an investigation into two explosions at the plant was currently ongoing.
It was already known that the plant had suffered boiler failure in early August, but the full extent of the problems has only now emerged .
The plant was temporarily shut down for repairs on 12 August and will remain closed until at least November.
‘Mistrust and fear’
Linda Holt, of Mossmorran Action Group, said an HSE official had described the incident as a “catastrophic breakdown” at a working group meeting earlier.
Ms Holt said she was “shocked” to learn that the two boiler breakdowns in August were both accompanied by explosions.
She added: “We were also told that neither HSE nor Exxon have so far identified the cause.
“Rumours have been circulating locally that the boilers exploded, and HSE’s confirmation makes a mockery of ExxonMobil’s communication strategy.
“For years local communities have lived with the fear of an accident at the plant; trying to hide explosions behind an announcement of £140m investment will only exacerbate local mistrust and fear.”
In July, the plant was issued with an improvement notice over the risk of an explosion.
At the time the HSE said ExxonMobil had failed to take all measures necessary to reduce the risk of “firebox explosion from furnaces”.
The firebox is an area in the plant’s furnaces where fuel is burnt.