Investigators have determined that the cause of the fire at Robbins Lumber in Searsmont was accidental and believe it stemmed from an area near the base of a silo that exploded, killing one and injuring a dozen others.

Officials believe the fire began in an unloader mechanism at the base of the silo, Shannon Moss, a spokesperson for the Maine Department of Public Safety, said in a news release Tuesday.

“Before fire suppression operations could fully contain the smoldering fire, a rapid ignition of suspended particulate material resulted in an explosion within the silo,” Moss stated.

The fire and explosion on May 15 resulted in the death of Morrill volunteer firefighter Andrew Cross, 27. Among the dozen injured were other first responders and mill employees.

Investigators determined that the silo was lifted from its concrete base during the explosion, releasing sawdust and additional materials, Moss said. The silo then toppled and the surrounding area became engulfed in flames, Moss said, spreading to nearby structures within the mill complex.

A fire suppression system located near the top of the silo did not activate, Moss said, as temperatures at that elevation did not reach the system’s activation threshold.

Over the weekend, cranes were utilized to lift and move the silo, Moss said, allowing officials to access key areas to the investigation.

The Office of the State Fire Marshal and the Bureau of Alcohol, Tobacco, Firearms and Explosives National Response Team completed their initial on-scene investigation and began demobilizing on Monday, Moss said, but the investigation is still ongoing. Investigators will return to the facility for a more detailed examination of the unloader systems in the coming months, Moss said.

Officials have also initiated a line-of-duty death review process, Moss said, and the fire marshal’s office is coordinating with the National Institute for Occupational Safety and Health regarding firefighter safety.

Moss said investigators also determined that one of those injured, John Ward, responded to the scene as a member of the Lincolnville Fire Department. Initial statements from officials indicated Ward had been a mill employee.

First responders were first dispatched to Robbins Lumber in Searsmont on May 15 at around 10:05 a.m. for a fire. About an hour later, the explosion drew firefighters from departments across Waldo County and beyond, in addition to state agencies.

Following news of Cross’s death, condolences poured in from across the state. Various fundraisers for those impacted by the incident had raised hundreds of thousands of dollars combined within a week.