ELGIN, Ill. (CBS) — Police and fire investigators said Thursday they need the public’s help in determining who is responsible for a weekend fire at the iconic, but endangered, Tower Building in downtown Elgin.

Six investigators have been working the case — three police detectives and three fire investigators.

Elgin Fire Department Battalion Chief Terrance Bruce said the fire is considered suspicious because first responders found the lobby door glass broken out.

“Given the circumstances of the broken door and the history of the building, unoccupied at the time, we’re concerned as to what happened to cause this fire to start,” Bruce said.

Elgin Police Cmdr. Dan O’Shea refused to say if any security cameras captured the break-in or fire.

Bruce said the fire was put out quickly and damage was relatively minor, but it left the already-troubled building without working elevators and uninhabitable.

The foundation that owns the building has said the building will be sold. City building inspectors said, without repairs, it could be condemned.

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