BALTIMORE (WJZ) — One day after firefighters Lt. Paul Butrim, Firefighters Kelsey Sadler and Kenny Lacayo died in the line of duty, Maryland State Fire Marshal Brian Geraci is back on the scene of the fire on South Stricker Street.

“It’s obviously a very sad day, we are all heartbroken,” Geraci said. “The Maryland fire service hearts are broken for this tragic loss.”

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The rubble at the site of the fire was still emitting smoke in some areas. The investigation could be an uphill battle because along with the collapse, there aren’t many witnesses or videos of what happened Monday morning.

Geraci said Baltimore fire investigators and members of the ATF are sifting through what’s left of the partially collapsed building to get additional details for their investigation.

Geraci said investigators are looking for any clues like where the fire may have started and what the burn patterns are. They will even revisit a fire from back in 2015 at the same vacant rowhome on South Stricker Street. Three firefighters were injured back then.

“Going back and talking to those folks from the 2015 fire as well to see just exactly what took place there as well. We can try to compare to see damage wise, in 2015, where that fire was, those type of things compared to yesterday,” says Geraci.

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The fire marshall also theorized a homeless person may have set a warming fire that got out of control.

A total of four firefighters were trapped Monday when a portion of the building collapsed. The state fire marshal said it is too early to determine if someone set this fire on purpose so that they could hurt others.

In addition to the three victims who died, another firefighter, John McMaster, was placed on life support at Shock Trauma. Fire Chief Niles Ford said McMaster was upgraded to fair condition Tuesday. His sister told WJZ he’s even talking.

“While he has a long way to go, I am incredibly optimistic, and we will continue to pray for and support EMT/FF McMaster and his family during his time of recovery,” Chief Ford said.

The state fire marshal said it could take months or even years for the investigators to determine the cause of fires and in some cases, no cause is determined.

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Annie Rose Ramos contributed to this report

Ava-joye Burnett