A deluge of 999 calls were made to the fire service and police as Mossmorran continued to flare on Friday night.
People feared the illuminated sky and huge flare at the petrochemical plant near Cowdenbeath which could be seen from miles around was a massive fire.
Among those horrified at the sight was leading crime writer Ian Rankin who said footage of the plant “looks like hell”.
Operator ExxonMobil Chemical said on Saturday morning the plant had returned to normal operation following the latest episode of unplanned flaring, which lasted six days and prompted hundreds of complaints.
Police Scotland tweeted to offer reassurance to the worried public that what they were seeing was elevated flaring at Fife Ethylene Plant.
Late on Friday evening, it said: “The Scottish Fire and Rescue Service and ourselves are receiving numerous calls re large fires in Fife.
“This has been confirmed as flaring at Mossmorran, and there are no issues.”
Good Evening, the Scottish Fire and Rescue Service and ourselves are receiving numerous calls re large fires in Fife. This has been confirmed as `flaring` at Mossmorran, and there are no issues. @fire_scot @exxonmobil
— Police Scotland Control Rooms (@polscotcontrol) April 26, 2019
Rankin, who grew up in nearby Cardenden and is famous for his Inspector Rebus series, retweeted a video taken by Claire Graham on Thursday showing flames roaring from the site.
This looks like hell… https://t.co/D1lf3fveIe
— Ian Rankin (@Beathhigh) April 26, 2019
Elevated flaring is a safety mechanism used during process upsets at the plant, but there are widespread fears about it becoming more frequent and more disruptive.
A statement issued by ExxonMobil at 8.30am on Saturday said the elevated flaring had come to an end but ground flaring would continue.
It said: “At approximately 2300 last night our team returned the plant safely to normal operations. Elevated flaring has now ended.
“As we move up to full process rates a small amount of ground flaring above normal levels will be required for a short period.
“We are already undertaking our investigation into this unplanned event, focusing on root cause, corrective action and evaluation of ways to continuously improve our response following a process upset.
“Furthermore, we will next week submit to Sepa our best available techniques report, which will set a pathway to further minimise unplanned flaring events.
“We are committed to sharing more information as our investigation continues.”
Sepa, which issued final warning letters following “preventable and unacceptable” flaring in April last year, has already launched a full investigation.
It has been monitoring air quality and noise since the episode began on Sunday.
By Thursday it had received 600 complaints about the flaring, the most ever for a single incident.
Chief executive officer Terry A’Hearn said then: “The Mossmorran complex is a major industrial facility, where this type of flaring is a legitimate safety mechanism, but it’s been happening too often, and the current level and extent of the flaring from ExxonMobil Chemical Limited is unacceptable.”