NOISE from the Mossmorran Fife Ethylene Plant on Friday night led to complaints from people in Cowdenbeath and Lochgelly.
Sepa confirmed it had received numerous complaints indicating noise was similar to a severe rumbling.
They tweeted: "Late this evening we’ve received a number of complaints regarding noise at ExxonMobil, Mossmorran.
"Officers have contacted the site and understand the site is working through routine de-coking activity".
Linda Holt of the Mossmorran Action Group said: "We're getting reports of extreme noise at Mossmorran this evening.
"Please, please report to SEPA. The only reason that SEPA is pursuing court action against Exxon, and the only reason the Scottish Government is taking the notice that it is, is the volume of complaints last year to SEPA. Please complain if you are being affected".
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here