The cause of the blaze was not immediately clear.
CNN  — 

A structure fire at an ExxonMobil refinery in Montana burned for more than three hours, officials said Sunday.

“Last night, our Billings Refinery personnel responded to a fire at one of our units at approximately 9:50 p.m. The fire was reported out at about 1:15 a.m.,” ExxonMobil Operations Media Manager Julie L. King told CNN.

“There were no injuries, and air monitoring in the community showed no adverse readings from the fire.”

Fire departments in Billings and Lockwood, Montana, responded to the scene, the Billings Fire Department tweeted.

King said the cause of the fire has not been determined.

“We are working diligently to better understand the incident and continue to cooperate with authorities,” she said.

“Our main priority is the safety of our workforce and the community. We are sorry this incident has occurred and apologize for any disruption or inconvenience.”

The refinery is located on the bank of the Yellowstone River near Lockwood, Montana, according to the ExxonMobil website.

It covers 720 acres, which includes about 370 acres of undeveloped land and urban wildlife habitat area, according to the website.

CNN’s Holly Yan contributed to this report.