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.

Federal prosecutors have filed charges against a former Army serviceman they accused of distributing instructions on how to build explosives that were used by a man who conducted a deadly attack in New Orleans on New Year’s Day last year.

The former serviceman, Jordan A. Derrick, a 40-year-old from Missouri, was charged with one count of engaging in the business of manufacturing explosive materials without a license; one count of unlawful possession of an unregistered destructive device; and one count of distributing information relating to manufacturing explosives, according to a criminal complaint unsealed on Wednesday. The three charges together carry a maximum sentence of 40 years in federal prison.

Starting in September 2023, the authorities said, Mr. Derrick was using various social media sites to share videos of himself making explosive materials, including detonators. His videos provided step-by-step instructions, and he often engaged with viewers in comments, sometimes answering their questions about the chemistry behind the explosives.

The authorities said that Mr. Derrick’s videos were downloaded by Shamsud-Din Bahar Jabbar, 42, who was accused of ramming a pickup truck into a crowd on Bourbon Street in New Orleans on Jan. 1, 2025, in a terrorist attack that killed 14 people and injured dozens. Mr. Jabbar was killed in a shootout with the police. Before the attack, Mr. Jabbar had placed two explosives on Bourbon Street, the authorities said, but they did not detonate.

The authorities later recovered two laptops and a USB drive in a house that Mr. Jabbar had rented. The USB drive contained several videos created by Mr. Derrick that provided instructions on making explosives. The authorities said the explosives they recovered were consistent with the ones Mr. Derrick had posted about.

Mr. Derrick’s lawyers did not respond to requests for comment.

Mr. Derrick was a combat engineer in the Army, where he provided personnel and vehicle support, the authorities said. He also helped supervise safety personnel during demolitions and various operations. He was honorably discharged in February 2013.

The authorities did not say whether Mr. Derrick had any communication with Mr. Jabbar, or whether the men had known each other. In some of Mr. Derrick’s videos and comments, he indicated that he was aware that his videos could be misused.

“There are a plethora of uh, moral, you know, entanglements with topics, any topic of teaching explosives, right?” he asked in one video, according to the affidavit. “Of course, the wrong people could get it.”

The authorities also said that an explosion occurred at a private residence in Odessa, Mo., on May 4, and the occupant of the residence told investigators that he had manufactured explosives after watching online tutorials from Mr. Derrick.

Mr. Derrick’s YouTube account had more than 15,000 subscribers and 20 published videos, the affidavit said. He had also posted content on other platforms, including Odysee and Patreon. Some videos were accessible to the public for free, while others required a paid subscription to view.

“My responsibility to my countrymen is to make sure that I serve the function of the Second Amendment to strengthen it,” Mr. Derrick said in one of his videos, according to the affidavit. “This is how I serve my country for real.”

Outside of the income he received through content creation, Mr. Derrick did not have any known employment. He did receive a monthly disability check from Veterans Affairs, the affidavit stated.