An investigation into unplanned flaring at Mossmorran could result in a criminal prosecution, if evidence is found to support it.
Environment watchdog Sepa said the probe into prolonged unplanned flaring at Fife Ethylene Plant (FEP) last April, was nearing its final stages.
Speaking at Friday’s public meeting, Sepa’s head of environmental performance, Chris Dailly, said: “It’s a criminal investigation carried out to an evidential standard and is very detailed.
“We’re approaching the stage where we will be able to confirm the outcome of that but not quite yet.”
Adding that the investigation was “incredibly complex”, he said: “If there is any possibility we’re likely to refer a report to the fiscal it has to be meticulous, it has to be detailed and it takes time.”
Mr Dailly added that Sepa had the power to vary Exxon’s operating permit but that it would only be removed in exceptional circumstances.
“Flaring is an essential safety mechanism and will happen in the future but with the investment being carried out, it should happen less often and, when it does need to happen, it should not be felt in the way it has been.”
FEP operators ExxonMobil announced on Friday afternoon that the plant had resumed normal production after a six-month closure.
Plant manager Jacob McAlister said the plant had restarted safely and that processes and safety procedures had been fully tested.
The plant had been closed for maintenance since August when two out of three boilers failed.
ExxonMobil had hoped the plant would reopen before Christmas but Mr McAlister said the process had taken longer than expected.
“We will never compromise the safety of our staff or the public,” he said.
“The additional work we have conducted during the temporary shut-down is designed to help improve operational reliability and reduce the requirement for unplanned flaring.”
Friday’s public meeting was prompted by an episode of “apocalyptic” flaring as Exxon attempted to restart the plant.
The company said it would not attend the meeting as it did not believe it would receive a fair hearing.