Witnesses say they heard a loud boom when the fire erupted Wednesday night just after 10 p.m.
"It was very hot, extremely hot," Maria Espinosa said. "The fire was 80…they say it was so high, all the sparks were just shooting."
The townhome buildings that were burning were under construction and empty, but firefighters were concerned about the occupied buildings surrounding the fire.
"There was a large volume of fire directly impacting unburned buildings and we were able to get a large amt of water between fire and buildings that weren't burning," Santa Clara Fire Department Batt. Chief Mason Weirshauser said.
Residents did what they could to help.
"I grabbed my hose and started hosing my roof because it's wood; the thing was in flames, I've never seen anything like that," Espinosa said.
Firefighters went to a fifth alarm in order to try and save the buildings around the fire. Two townhome units were damaged, but the other buildings are still intact. Firefighters are calling that a success.
"The mutual aid system worked as it's supposed to," Weirshauser said."We got resources to the scene quickly as well as resources to cover our city because our fire department was pretty tapped out at that point."
Now the focus is on finding a cause. Investigators started early Thursday morning in their quest to find out what started the fire. They are also working to try and get evacuated residents back into their homes.
"We're restoring the fire alarm system and the water system, so they can return, hopefully, later today," Santa Clara Fire Department Batt. Chief Randy Titus said.
The builder says he also has no idea what could have started the fire.