LAS VEGAS (KLAS) — The cause of a massive fire that destroyed an apartment complex under construction has been ruled “undetermined,” according to the Clark County Fire Department.

Fire investigators don’t know what caused the fire on June 20, 2023, that left a massive complex on Maule Avenue near S. Buffalo Drive and the 215 Beltway in ruins.

“We were not able to make a conclusive determination because we were not able to identify a competent heat source or the first material ignited and you can not make a determination without those two things,” Clark County Fire Department Assistant Chief Carlito Rayos said.

What Rayos is confident about is no evidence was found to indicate the fire was arson.

Clark County Fire Department Assistant Chief Carlito Rayos discusses a fire that destroyed an apartment building complex that was under construction. (KLAS)

“We explored every avenue we could and sometimes the evidence is just not there. We believe that is because of the severity and duration of this fire,” Rayos said.

He added the fire started on the roof of the five-story Building D.

“It was in close proximity to Independence Day so could this have been a firework? We canvassed the entire neighborhood and everybody that had a balcony, facing this property, we knocked on the door and talked to them.”

Nevada State Police release a photo taken of the apartment building fire in southwest Las Vegas on June 20, 2023. (NSP)

Fire Chief John Steinbeck gave a timeline of the fire which was first reported at 4:28 p.m. and said within five minutes, the first fire truck was at the scene. It became obvious quickly that the fire was so intense that units from North Las Vegas, Las Vegas, and Henderson also responded.

Steinbeck said by 4:44 p.m., it was clear Building D could not be saved so firefighters focused on attempting to save the other buildings as winds fanned the flames and even jumped the 215 Beltway. Within minutes the fire spread to other structures and “significantly damaged” one of the first trucks at the scene.

He said any building under construction is tough to save.

“When I drive by them in the wood frame, the hair stands up on the back of my neck. My experience shows these stick fires, we always lose them. They overrun us.”

Steinback said the developer plans to rebuild the $90 million apartment complex.