WICHITA, Kan. (KSNW) — The Wichita Fire Department (WFD) says it knows what started the three-alarm fire at an apartment complex in west Wichita Tuesday.

Battalion Chief Jose Ocadiz says a resident had been smoking on a balcony and carelessly discarded the cigarette. After the fire started, it rolled over the covered balcony and entered the building through the soffit. It eventually made its way into the attic space.

The fire caused $2 million in damage and burned the homes of 20 people.

A firefighter who was transported to a hospital with serious injuries remains hospitalized Wednesday. On Tuesday evening, a WFD spokesperson said the firefighter was upgraded to a “moderate medical emergency.” Ocadiz says the firefighter is being monitored.

Around 6:20 p.m., the WFD was dispatched to the Aspen Park Apartments located in the 8400 block of W Central Ave. As the crews arrived on the scene, a big plume of smoke could be seen coming from the apartments.

Fire crews managed to contain the fire to one building. Investigators say the building may be a loss, but they do not know the extent of the damage. The roof was severely burned and damaged.

Ocadiz said firefighters searched the entire building and did not find anyone still inside.

Crews continued to work the scene throughout the night. In addition, EMS was on the scene to offer hydration and give relief to fire crews due to high temperatures.

According to the Red Cross, the fire destroyed at least 14 of the 16 units. The Red Cross is assisting the victims.