SAN JOSE (KGO) -- Arson investigators are looking in the cause of a late night fire in San Jose that kept spreading through a neighborhood.
It began at a house under construction, but quickly spread to three other homes.
The fire was reported just before 8:15 Wednesday night at Ellis Avenue in Willow Glen.
The blaze eventually turned into a three alarm fire; two adjacent homes were damaged on their sides. Firefighters said those people initially evacuated, but they'll eventually be able to get back in.
About an hour later, another nearby home caught fire. The roof caught fire from some embers that floated away from the original scene.
In the end, four structures were damaged and everything was brought under control about an hour and 45 minutes after the first call.
The biggest concern of this investigation is the possibility the home under construction could collapse.
ABC7 News heard from neighbors who called 911 for the first time on Thursday.
Video from San Jose fire photographer Craig Rose showed the firefighters battling the flames in a defensive position.
They knew the house under construction was a lost cause, but the two homes next to it needed saving.
One of those homes belongs to the Ganz family. "We were just watching a TV show and my grandma yelled, 'the house is on fire,'" neighbor Stella Saglimbeni said.
"Then it was just running, grabbing the dog, heading across the street. The neighbors were all collecting us, the flames were literally already at that point to the top of the third story roof," Erica Ganz said.
The Ganz family home was singed, but saved.
Investigators are working to figure out what started this fire.
Officials said the project manager of the home under construction cooperated with investigators.
Neighbors said the lot has been under construction for more than a year and in all that time it had only been framed.
When the project manager was asked why it has been taking so long to finish the home, he said he didn't know why.
Arson investigators told ABC7 News they'll look into the finances and insurance policies of the owners.
Investigators also brought a fire investigating dog from Sunnyvale who had some interest in some spots.
Investigators took samples, but said it's not uncommon to have these types of materials on a construction site.
Fire investigators are asking neighbors for any surveillance video they may have, but said a final conclusion on this investigation could take months.