PHOENIX - A year and a half ago, a house explosion near Piestewa Peak shook an entire neighborhood, leaving residents and fire investigators puzzled over the cause.
It was a multi-million dollar home that was built into the mountain near 36th Street and Lincoln - and it was ultimately leveled on Feb. 6, 2022.
Fire officials said in February 2023 that the evidence was literally blown to pieces, making it difficult for them to put together what happened.
"We've got to start piece by piece - we have to work with structural engineers to start pulling apart the house for us - we had to pull apart the yard to look at those pipes," said Phoenix Fire Captain Rob McDade.
Now, the Phoenix Fire Department concluded its investigation, finding the fire was a mechanical failure tied to the home's propane tank.
This wasn't the typical small propane tank that many people use to fuel outdoor grills.
Officials say this 5,000 square-foot home had a 500-gallon propane tank that had a leak and completely filled the home. The home was not served by Southwest Gas and reportedly ran completely off the tank.
"The pipes from the propane leading into the home had severe oxidation," said the fire captain. "The degradation of them led to them being allowed to fill the home with propane gas. Dangerous levels of propane gas."
They still don't know what ignited the propane because no one was home at the time, but they do not believe it was suspicious. An arson dog was brought to the home and found no sign of accelerants or foul play.
McDade called this "the perfect storm."
"There was an unbelievable amount of destruction with that home, almost akin to a bomb going off," McDade said.
The homeowners weren't home at the time, or they would have smelled what was happening, the fire captain said. But neighbors saw and felt the whole thing.
"I had 13 of these windows replaced. I was looking there and I thought, 'I really am losing it. That window is coming in,'" said Betty Bool, a neighbor. "One second later - the noise. By the time the explosion happened - the windows didn't fall in - they fell out."
Nine homes surrounding it had their windows blown out, and a few neighbors reported headaches and concussions from the blast.
The fire department says it's not uncommon for homes in the Phoenix area to rely on whole-home propane tanks. Authorities are advising residents who have one to have it checked and serviced regularly to prevent events like this from happening.
We reached out to the homeowners who still own the property, but they did not comment.