An explosion and fire drew a large emergency response on Friday to a lumber mill in the Midcoast region of Maine, officials said.

The State Police and fire marshal’s investigators responded to Robbins Lumber in Searsmont, about 72 miles northeast of Portland, said Shannon Moss, a spokeswoman for the Maine Department of Public Safety.

Mike Larrivee, the director of the Waldo County Regional Communications Center, said the number of victims was unknown, cautioning that “the information we’re getting from the scene is very vague.”

“We’ve sent every resource in the county to that area, plus surrounding counties,” he said.

Footage from the scene shared by WABI-TV showed flames burning through the roof of a large structure as heavy, dark smoke billowed skyward.

The Associated Press reported that at least five people were injured, and that county officials were considering the incident a “mass casualty event.”

Catherine Robbins-Halsted, an owner and vice president at Robbins Lumber, told reporters at the scene that all of the company’s employees had been accounted for.

Gov. Janet T. Mills of Maine said on social media that she had been briefed on the situation and urged people to avoid the area.

“I ask Maine people to join me in keeping all those affected in their thoughts,” she said.

Representative Jared Golden, Democrat of Maine, said on social media that he was aware of the fire and explosion.

“As my team and I seek out more information, I am praying for the safety and well-being of first responders and everyone else on-site,” he said.

This is a developing story. Check back for updates.