With more than 94 percent the precincts reporting as of Wednesday morning, voters rejected Proposition 37, the San Francisco Chronicle reported.
Opponents of the measure, which would have required genetically engineered foods to include labels on either the front or back of the product, argued the price of new labels, or the cost manufacturers will incur by changing over to non-GMO ingredients, would be passed on to consumers.
"We said from the beginning that the more voters learned about Prop. 37, the less they would like it," said Kathy Fairbanks, a spokeswoman for the opposition. "We didn't think they would like the lawsuits, more bureaucracy, higher costs, loopholes and exemptions. It looks like they don't."
If the measure had passed, California would have been the first state in the nation to pass such an initiative.
"Whatever happens tonight, this is a win," said Grant Lundberg, chief executive officer of Lundberg Family Farms, co-chair of Yes on 37. "Never before have millions of Californians come together to support giving consumers a choice about genetically engineered foods."