CHICAGO — The cause of the death for the Chicago fire lieutenant who passed away Wednesday morning has been revealed.

The Cook County Medical Examiner’s Office revealed that 55-year-old Jan Tchoryk died from natural causes due to hypertensive-arteriosclerotic cardiovascular disease.

The Chicago Fire Department dispatched crews to the 1200 block of North Lake Shore Drive just before 7:30 a.m. Wednesday on a still-and-box response. A short time later, a mayday response was called for a firefighter down.

The Chicago Fire Department said Lt. Jan Tchoryk was making his way up the stairs to the 27th floor when he went down at the 11th floor.

He was rushed by colleagues to the lobby where life-saving measures were performed. He died as a result of his injuries, CFD said.

The CFD said the fire was initially out and they were just battling hot spots. However just before 9 a.m. Wednesday, the fire reignited and large flames were shooting out of another unit.

CFD lost the ability to use elevators and said there are no sprinklers on any of the residential floors of the building.

The cause of the fire was ultimately determined to be accidental due to “combustibles being too close to a heat generating appliance,” The Chicago Fire Department released Thursday.

CFD said Tchoryk was an active outdoorsman, an avid motorcyclist, a Navy veteran and comes from a large family. His son recently joined The Chicago Police Department as an officer.

Stay with WGN as this story develops.