EVERETT — Firefighters knew they had a potential problem at the recycling business that erupted into a massive fire Saturday evening.

Twice last week they were summoned to small fires that filled the building with smoke, Everett Fire Marshal Eric Hicks said Sunday.

On Thursday, the fire department told the company it wanted to develop a plan for storing fire-prone materials outside the structure, he said.

“We were going to work on that with them this week,” Hicks said.

Saturday’s fire consumed the building, sending up flames that reached 50 feet high and unleashing a plume of dark smoke.

Smoke continued to climb from the site Sunday while firefighters kept watch for rekindled flames.

Concern over the safety at the site dates back years.

The 7-acre industrial lot where the fire started on Marine View Drive was the location of a recycling business that was shut down by authorities in 2014 over health and safety concerns. The lot belongs to a limited liability company that had rented the location for business use, according to property records.

Thousands of tons of ground-up asphalt shingles were stored at the site, according to the Snohomish Health District.

The previous tenant, known as Busy Beaver Recycling, had a pile of about 70,000 tons of material, primarily ground-up shingles stored outside, said Heather Thomas, a health district spokeswoman.

The health district went to court two years ago because the shingles were not allowed under the recycling facility’s permit, Thomas said.

The property owners, meanwhile, also began litigation, trying to force the former tenant to clean up the mess. That case was still working its way through the courts last week.

“The property owner was stuck with the material,” the health district’s Thomas said. “So we worked with him. His solution was to move it inside the building.”

The only way to safely dispose of the material was to take it to a landfill, which would have cost millions of dollars. Moving the materials inside was considered a temporary solution pending further action by the property owner, Thomas said.

The property was former site of the Weyerhaeuser pulp plant that closed in 1992, among other uses.

Saturday’s fire broke out just before 7 p.m. Two walls and the roof collapsed from the fire’s intensity. At the peak of the response, about 90 firefighters were at the scene from throughout Snohomish County, including Lynnwood, Marysville and Monroe.

On Sunday, crews were on the scene to fight spot fires and smoldering areas inside the building.

Hicks said it was too early to calculate the financial loss, but damage to the building alone “will be in the seven figures.”

Hicks said fire officials didn’t get the chance to confirm all of what was inside the structure, but he knew the flames Saturday were fed by wood pallets, plastics and other material.

First-arriving crews went inside, but the fire roared to life quickly.

“Luckily, they got out in time before it did erupt,” he said.

As firefighters continued to douse the smoldering structure Sunday, people walked to an overlook on Marine View Drive to take in the scene.

John Scherz of Everett is a machinist at Everett Engineering. The company is located in a building next to the one that burned. Crews battled to ensure that it didn’t spread to it, too.

Scherz was allowed to briefly peek into the Everett Engineering building on Sunday. He said he saw some structural damage and a lot of water damage.

Still, firefighters “did a great job,” he said. “They saved that business for sure.”

Linda Lacey, who lives on Rucker Hill, said she heard a loud boom Saturday night just before the flames erupted. She initially thought a plane had crashed. She drove to get a closer look. “I was shaking all the way down here,” she said.

Scott Fisher and his wife, Stacy Fisher, were attending a wedding in Snohomish on Saturday evening. The plume of smoke was so dark and so large that he said it reminded him of a volcanic eruption.

Jim Cory and his wife, Jackie Cory, stopped for a close-up view Sunday. “We wanted to see what it looks like,” he said. Jim Cory was familiar with the area. He said he had once worked a summer job at the former Weyerhaeuser pulp plant.

Pete Chandler, of Snohomish, said he could see the long black plume of smoke at his house heading south. Friends in Kirkland and Bellevue said they could see it too, he said.

“The last big fire like this was the Everett tire fire” in 1984, Chandler said, as he took in the scene on Sunday. “Thank God no one was hurt. It’s pretty scary stuff.”

Sharon Salyer: 425-39-3486; salyer@heraldnet.com.