Habitat for Humanity says the thieves broke their gate, smashed surveillance cameras and cut their telephone lines. The thieves then stole table saws, drills and paint sprayers; a loss of about $40,000.
Some say the burglars knew what they were doing because they stole the most expensive equipment on the construction site.
Dozens of families waiting to move in say the news is heartbreaking.
"It's hurtful because it's my dream to own a home, and being that ... you could say that they're kind of stealing from my dream because those are the tools they're going to use to build my home with," said Darcy Ortega, future Habitat for Humanity homeowner.
"It's devastating," said Joyce Grair, Habitat for Humanity. "I can't believe someone would do this to a nonprofit, you know, steal from us. And we're trying to better the community and help the families that need help ... And someone would do this."
Habitat for Humanity is building 42 new homes on the Pacoima site. Another 20 homes are already completed on the next block. The group says this won't slow them down and that they now have extra security.
Darcy Ortega's family is living in a small one bedroom apartment and her new home will mean a better place for her children. However, this theft is something she never expected.
"It's a good organization ... Habitat ... they're doing something for the community. For someone to steal from the community is ... it is ... it's hard to hear that," said Darcy.
Since the thieves took heavy items, some say there must have been three or four people working together. The group is asking any witnesses to report if they saw any unusual activity. If you have any information, you should call the Los Angeles Police Department Foothill Division at (818) 756-8861.
Habitat for Humanity says they will continue working and will have the houses ready as quickly as possible.