Residents have been raising concerns about large flames and smoke coming from the Mossmorran Petrochemical Plant last night.
People living in Kelty, Cowdenbeath and Lochgelly say they fear the an incident could be damaging to their health.
Black smoke could be seen for miles yesterday evening, with some claiming they could smell burning throughout the night.
It comes just a week after emergency flaring at Mossmorran brought fresh calls for bosses to provide proof it was safe for people living nearby.
Last night's incident incident is not related to the ongoing flaring last week.
Chris Warmer lives in Kelty, and could see flames and smoke from his back garden:
A spokesperson for ExxonMobil, which operates the plant, said: "ExxonMobil Chemical Limited apologises to the local communities for the flaring at the Fife Ethylene Plant, Mossmorran.
"The flare is an essential part of the plant’s safety systems and there is no danger to local communities or employees.
"This flaring is the result of a sudden, temporary disruption to the feedstock process for the plant during the evening of Sunday 18th June.
"This flaring is a separate issue from last week’s process upset, which was resolved on Saturday at 9:20am.
"We aim to keep flaring to a minimum and are currently in the process of resuming normal operations.
"We anticipate completion within the next 36 hours."