Bosses at Mossmorran have insisted work is continuing “round the clock” to restore normality after flaring resumed over the weekend.
ExxonMobil Chemical said it hoped to return to normal operations within two days following the failure of a pump at the Fife ethylene plant on Saturday.
Green MSP Mark Ruskell has hit out at the plant for heaping “more misery on the local community.
The latest incident comes just weeks after ExxonMobil Chemical and fellow site operator Shell UK were given a final warning by environmental watchdog Sepa following prolonged flaring last June.
Sepa is currently investigating two further instances of unplanned flaring.
The Mid Scotland and Fife MSP said the latest flaring demonstrated a “staggering level of arrogance” from the businesses behind Mossmorran.
“Sepa identified maintenance failures when they issued these final warnings in April,” said Mr Ruskell.
“With another two incidents still under investigation, in addition to this latest, it is vital that significant enforcement action is taken by the regulator.
“My constituents living in the shadow of the plant are understandably angry that their lives are being made a misery, with ever increasing regularity.
“If Sepa expects to be taken seriously they must ensure that ‘final warning’ means just that,” he added.
ExxonMobil Chemical FEP plant manager Sonia Bingham said good progress was being made as a maintenance team and specialist supplier work around the clock to resolve the issue.
The failed pump — one of more than 200 at the plant — is being repaired using spares.
“Providing there are no complications, we expect to resume normal operations within two days,” she said.
ExxonMobil is conducting noise monitoring in the local communities.
Sepa is also monitoring air quality and noise levels and said early indications showed air quality levels “are consistent with our expectations”.
Ms Bingham said flaring was an essential part of the plant’s safety systems and there was no danger to local communities or employee.
“Safety and environmental protection are our highest priorities and we will do all we can to keep flaring to a minimum,” she said.
“We are working closely with Sepa as we resolve the issue.
“We apologise to local communities for any disturbance and are in contact with local agencies and community groups to ensure local residents are kept informed.”