ST. LOUIS COUNTY, Mo. – Explosions like we witnessed Monday morning in north St. Louis County ignite questions. Ed Nordskog searches for the answers.

“There's all these bizarre possibilities that we have to consider, and a technical investigation starts to eliminate each one, until you're left with just the one that caused it” said Nordskog, a longtime bomb and arson investigator and profiler with the Los Angeles County Sheriff’s Department.

Nordskog says investigators start by finding the piece of debris that flew farthest. Then they extend the scene up to a few hundred yards, creating a 360-degree perimeter around the center of the blast.

“They'll study the direction that the blast went, primarily. Then they'll study the debris field, how big it is, where's the bulk of it?” he said. “And working backwards, and I saw the pictures of the structure, it's going to take a long time to go layer by layer through that to the to the floor.”

Meanwhile, detectives interview those closest to the scene at the time of the blast, followed by first responders.

“We study our victims quite a bit, so one or two of the investigators will focus on the people that live at this property,” Nordskog said. “You know, if they're victims, what about their lifestyle may have led up to this. It's not victim blaming, but you're taking in all the possible data.”

Nordskog reviewed our video of the scene and shared his professional opinion on what he believes may have fueled the explosion.

“My first impression, just looking at the images, the damage is consistent with a natural gas [explosion]. When you have an ignition or an explosion of the natural gas, the home comes apart in that old cartoon term ‘smithereens,’ lots of little pieces, so not many big pieces, but lots of little pieces. And that's consistent, and they tend to go up,” he said.

How important is it for investigators, especially in these early stages, to avoid any preconceptions about what they think may have happened? Do they have to lean on that a little bit as they work to find a direction? How do they balance those things?

“Well, that's the ethical dilemma in our field. I'll just tell you at first glance, this looks like a natural gas event, but that's just at first glance. And these guys are professionals that are going to come there to do this, they will understand that's what it looks like,” Nordskog said. “However, there are other possibilities, and a proper investigation of any fire or explosion is to consider all possibilities and then slowly eliminate each one by doing scene work.”

Nordskog says investigators focus on finding the right answers, not the fast answers.

“It's not going to happen tomorrow, and people want answers tomorrow, they're not going to get them tomorrow. It's going to take a long time, but if you do it right, and everything's answered correctly,” he said.

On Monday, Spire said its crews have found no issues with its gas-related infrastructure in the area, adding the utility would continue working with the fire department in their ongoing investigation. Authorities say the cause of Monday’s explosion is still unclear.