The Mossmorran chemical plant has been flaring once again today and the bright orange glow is visible for miles across Fife, Edinburgh and parts of the Lothians.
The environmental watchdog, SEPA, said they were notified of the unplanned flaring by plant operator ExxonMobil shortly before 3pm on Tuesday.
Bosses at the ethylene plant, located near Cowdenbeath and Lochgelly, say a "trip" in one of the major compressors is to blame and that they need to manage the process through an elevated flare to keep the rest of the plant running.
It comes after the plant was restarted two weeks ago after upgrades which cost £140 million. The plant was shut down last year following persistent flaring episodes.
A local action group has once again raised concerns about the repeated flaring and called on the Scottish Government to step in.
A community announcement posted on twitter this evening from plant manager, Jacob McAlister, said: "We have, unfortunately, experienced a trip on one of our major compressors. Our team is currently undertaking the necessary checks to begin a safe re-start. We apologise for any inconvenience.
"In order to keep the rest of the plant running and reduce total duration of flaring, we need to manage this process through our elevated flare. We are also working with our neighbours Shell to maximise ground flare capacity.
"The use of the flare is completely safe, and we will continue to keep you updated as we work our way through this process.
“We apologise for any inconvenience to our local communities."
In an earlier tweet, they described the cause of flaring as a "process upset."
Chris Dailly, head of Environmental Performance, said: "Having been clear that flaring must become the exception rather than routine, we’re disappointed that flaring by ExxonMobil Chemical Limited has occurred again so soon after the restart.
"Officers made immediate contact with the company and we understand that the flaring relates to a trip of a major compressor. In understanding that flaring is likely to continue overnight as the site moves to a safe re-start, officers will continue to deploy and air and noise monitoring continues.
“SEPA is requiring a detailed briefing on the nature of the current incident and we expect the company to provide timely updates to the community. Whilst recognising that flaring is an important safety mechanism, this is a further reminder of why the short and medium term steps being taken by SEPA to mitigate flaring is so critical, including noise-reducing flare tips in 2020/21 and bringing forward plans for fully enclosed ground flares."
Community expected to 'suffer in ignorance'
Speaking for the Mossmorran Action Group said, local councillor Linda Holt said: "Process upset and compressor trip explain nothing. Once again ExxonMobil is forced to resort to emergency flaring because something has gone badly wrong.
"As the ground shakes, and a huge bright flame amid clouds of black smoke looms over communities, they are expected to suffer in ignorance. SEPA expects the flaring to last all night but Exxon cannot say when it will stop.
"Since the 'catastrophic breakdown' of the plant last August which caused continual ground flaring, the problems restarting according to schedule, the 'apocalyptic flaring' a couple of weeks ago and a walk-out by workers over safety issues, neither ExxonMobil nor HSE nor SEPA have offered any explanation.
"Reassurances that the plant is 'safe' do not wash. A whistleblower told MAG two weeks ago that the plant restarted prematurely with only two out of three boilers and these were 'unfinished.'
"Is the Scottish Government waiting for a major accident before it steps in?"
The process of flaring involves burning off gas that cannot be processed. The site, which is shared by ExxonMobil Chemical Ltd and Shell Fife NGL, is used to produce ethylene.
Although the technique is legally permitted, it causes significant light and noise pollution which the operator is obliged to minimise.
In recent years, local residents have complained about unplanned flaring incidents leading to noise, disturbed sleep, light pollution and vibration.
SEPA has been asked for further comment in response to calls from the local action group.