After each ember is cooled — a process that can take days for large fires — the fire investigation starts. Our State Fire Marshal (SFM) division fire investigators step up when local fire or police departments ask for help determining the cause of a fire. Investigating fires is one of the most important things we do, and it's something we take very seriously. Our investigators take pride in doing a thorough and professional job.
“I don't want it to happen again, regardless of what happened," SFM fire investigator Jim Iammatteo said. “With each of these fire investigations, we're trying to prevent the next one."
However, those thorough investigations take time — sometimes days, weeks, months or even several years. The length of the investigation depends on dozens of variables, from the size of the scene to the weather. Sometimes the water that was used to put out the fire freezes, or pools in place and needs to be removed before debris can be examined. Each fire comes with its own safety hazards that investigators need to mitigate before they can examine evidence. The type of building, the number of jurisdictions involved and whether or not there is pending litigation can also make a difference in how long an investigation takes.
"We have to look at everything we can get our hands on, and the bigger the incident, the more we have to collect," Iammatteo said.
SFM investigators are working with evidence that is many times burned beyond recognition. They need to sift through ashes and dust to find what they are looking for — sometimes something as small as a grain of sand or liquids like gasoline. This evidence is then sent to a lab where it needs to be analyzed, another step that takes time.
Evidence isn't limited to what they find on the fire scene, either. Investigators may also use background information like financial transactions, cell phone records, alarm system data, witness statements, as well as other information to help determine what caused the fire. In each case, investigators carefully examine each piece of information to determine what really happened.
It's a complex job. Our investigators must follow the hundreds of guidelines in the most current edition of the National Fire Protection Association Guide for Fire and Explosion Investigations. They are also governed by Minnesota statutes, which limit what they can say publicly until an investigation is finished. They can't even share whether a fire was accidental or incendiary — which means it was set deliberately — until they have wrapped up the investigation completely.
To learn more about the important work our SFM division does for Minnesotans, visit our