The general manager of Northeast Agricultural Sales Inc. says a foreman violated company protocol by scraping a silo with a shovel, sparking an explosion Wednesday in Detroit that seriously injured the foreman and harmed two others.

When Anthony Tower, 62, of Newport used a shovel to scrape accumulated dust and sulfur off the top of an empty, 86-foot-tall silo used to store sulfur, he ignited the explosion, Justin Choiniere said Friday. The shovel hit an electrical wire on the silo, sparking a flash chemical fire, Choiniere said.

The correct protocol is to wash the silo with water and not “scrape it with a shovel,” Choiniere said.

“There’s training in place for what the procedure is to clean that hopper,” he said. “Protocol was not followed.”

Meanwhile, the Occupational Safety and Health Administration said it is inspecting Northeast Agricultural Sales, according to James Lally, a public affairs specialist at the U.S. Department of Labor. OSHA will determine which safety standards apply to the situation and whether the employer complied with those standards during the inspection, which can take up to six months. If it finds violations, it can issue citations and penalties.

According to records on its website, OSHA issued 10 citations against Northeast Agricultural Sales in April 2014 after an improperly stored fertilizer bin collapsed, injuring an employee. It’s not clear from the records how serious the injury was in that case.

The subsequent citations found various violations categorized as “serious,” including deficiencies in standards for machine guarding, transmission belts and wiring design. The company paid a total of $30,170 in fines.

On Wednesday, Clarence Rider, 36, of Pittsfield, also was working at the top of the silo at the time of the explosion. Lee Gustin, 50, of Cambridge, was working on the ground below.

When Tower’s clothing caught fire, Rider helped put out the fire before they both climbed to the ground, where Gustin assisted them, according to Steve McCausland, spokesman for the Maine Department of Public Safety.

Emergency officials arrived at the scene just before 2 p.m. Wednesday.

Tower was taken to Maine Medical Center in Portland by a LifeFlight helicopter for treatment of extensive burns. Rider and Gustin were treated at Sebasticook Valley Hospital in Pittsfield after complaining of respiratory problems.

The Department of Environmental Protection assessed any potential environmental threats to the area after the event, according to David Madore, director of communications, education and outreach.

Water used to extinguish the fire ran off into the site’s treatment lagoon. The department tested the runoff water and found that it had a neutral pH level, meaning that it does not pose an environmental threat.

The latest statement from McCausland said that investigators were continuing to work on what caused the spark at Northeast Agricultural Sales, which sells farm equipment off Route 100. McCausland said Friday he didn’t have any new information from the Office of State Fire Marshal, which is involved in the investigation. The fire marshal’s office did not return a call Friday.

Madeline St. Amour can be contacted at 861-9239 or at:

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Twitter: madelinestamour