SEATTLE – A Washington state ballot measure requiring mandatory labeling of genetically engineered foods is failing in early returns.

The campaign over Initiative 522 has been one of the costliest initiative fights in state history, drawing millions of dollars from out of state.

Early polling showed voters favored the measure. But a barrage of TV and radio spots financed by a food industry group and five biotechnology companies has helped narrow the gap.

The measure was failing 47 percent to 53 percent as the first votes were being counted Tuesday night.

If voters approve I-522, Washington would be the first state to put in place labeling requirements genetically modified foods.

Supporters say consumers have the right to know what’s in the food they buy, while opponents say the measure would lead to higher food costs.