EVELETH - Fires broke out at the former Days Inn hotel here on Wednesday, and again on Thursday and will again all weekend.

Arson investigators at the scene, dozens of them, are 100 percent sure that the fires were intentionally set. That's because they started them.

Fire investigator school is in session at the abandoned, dilapidated and tax-forfeited hotel that's destined for the wrecking ball later this year. Investigators from across Minnesota, the Midwest and as far away as South Africa are in town to set fires in dozens of the hotel's 144 rooms.

"We are fire investigators. We don't really like the title arson investigator because it assumes the cause of the fire ahead of time," said Jim Iammatteo, chief investigator for the Minnesota State Fire Marshal's Office and state director of the International Association of Arson Investigators. "We investigate a lot of fires and only some of them are arson. Some are accidents. Some are electrical. Some we never know."

Multiple scenarios are playing out in different rooms. In some cases, fires are being set that mimic fires already in the legal system - criminal and civil court cases - as investigators try to duplicate the claimed or suspected cause.

Agents from the Federal Bureau of Alcohol, Tobacco, Firearms and Explosives are here too, looking at how electrical fires jump, or don't, between wiring, called electric arc mapping. Private fire investigators, who often work for insurance companies, are here watching things such as burn patterns from cigarette fires.

Generators supply power where needed for experiments. Electricity has been cut for years to the 124,000-square-foot building so the hallways are dark, except for the sharp beams of firefighter's flashlights. There's a musty mildew smell wafting from the carpeting. Long-emptied vending machines sit like ghostly guards near entrances. Some windows are cracked or missing. Outside, weeds grow high among the many cracks in sidewalks and parking lots.

But this relic of the 1970s hospitality industry - built as a first-class Holiday Inn when the Iron Range was booming - makes the perfect place to set fires and put them out, over and over, in nearly identical conditions from room to room.

"Size is nice, we don't get a lot of real big structures like this. But the best part is that we're off on our own here. There aren't any houses or roads or businesses here, and we have space to work without (smoke or fire) bothering anyone," Iammatteo said.

Investigators are able to watch how each fire plays out before, during and after the smoke clears.

"When they ask us in court how we know, we can say 'because I saw it happen,' " Iammatteo said.

From both inside the hallways and outside in the parking lot, investigators watched and took photos as the fires crackled to life, with flames eventually spreading through the rooms, out the windows and lapping at the exterior of the building.

It's not just fire investigators getting a lesson, though. Front-line firefighters from across the Iron Range are here each day, from volunteer and full-time departments, ready to douse every fire that's lit. It's the kind of real-world practice firefighters don't often get, including allowing them to watch how fires spread before turning the nozzle on their water hose.

"Fires are burning dirtier, hotter and faster than just 40 years ago because pretty much everything in these rooms is made out of petroleum products," said Chris Clark, Virginia fire marshal and a coordinator of the hotel fire school.

All of those synthetic materials not only burn well but emit toxic fumes - toxic not just in the short-term for anyone who breathes them in (toxic fumes, not flames, cause many of the fatalities in fires) but also in the long-term. Firefighters now are dealing with increased cancer rates apparently caused by legacy chemical contact.

"We have to wash our gear after every fire now," Clark noted.

In addition to hotel room fires firefighters also are practicing on mattress fires, a fire in the atrium and kitchen fires.

"Kitchen fires are becoming a bigger part of our calls every year," said Allen Lewis, Virginia fire chief.

The specific scenario for each room's fire is printed near the door, along with instructions on how long firefighters are to wait before they begin their attack.

"In this room here the message is to wait three minutes after flashover," Clark said, showing off a garbage can with crumpled paper and foam rubber, what would be the start-point for the next fire.

Flashover is the point where the fire grows so hot, often over 1,000 degrees Fahrenheit, that items in the room begin to burst into flames. Things like curtains, bedspreads, mattresses and box springs, carpeting, chairs and much more get so hot that they combust. Combine oxygen with ample fuel and lots of heat and fire literally explodes, shattering windows.

In one room where federal agents placed electronic temperature sensors, a fire that started in a small plastic garbage can quickly spread. Within a few minutes the temperature at the ceiling of the room was 1,100 degrees and 800 degrees four feet above the floor.

"We get information that allows us to say, hey, we know the temperature was 900 degrees in that kind of fire, so how could you possibly have been in the room at the time?" Iammatteo said.

Taxes unpaid, building to come down by winter

St. Louis County makes abandoned, dilapidated, tax-forfeited houses available on a regular basis for firefighter training. But hotel complexes are very rare.

The former Days Inn is on Hat Trick Avenue, just off U.S. Highway 53 and next to the U.S. Hockey Hall of Fame. A Minneapolis real-estate website once listed the property for $750,000, noting it previously sold for $3.5 million as a working hotel. But there were no buyers; the structure is woefully beyond repair.

Taxes haven't been paid since 2011 and the former owner, Steve Carlson, owes the county $117,340.41 for unpaid taxes from 2012 through 2016, said Don Dicklich, county auditor. The complex was officially declared tax-forfeited last November.

Eveleth city officials hope the seven-acre hotel property, a rare large tract in Eveleth that's not owned by mining companies, would be attractive to developers, although no deal has been signed.

Tearing down the sprawling hotel structure that once housed an indoor pool, atrium and full-service restaurant called Lord Stanley's is expected to be expensive, estimated at up to $1 million, with the county and Iron Range Resources and Rehabilitation Board expected to share the cost.

Darren Jablonski, the county's planning director, said the county will officially advertise for demolition and disposal bids next week. It will take several weeks to get bids back and final approval by the county board and IRRRB.

"Or goal is to have the building down yet this fall, before winter," Jablonski said. "Hopefully, something good can go up there."