Voters in Oregon and Colorado turned down high-profile ballot initiatives this week that would have required labels on foods made with ingredients from genetically engineered crops.

The Colorado proposal was defeated by a 2-to-1 margin. It would have required companies to label packaged foods with GMO ingredients with the words "produced with genetic engineering."

Oregon's ballot measure lost narrowly, and would have required the labels to include the words "genetically engineered."

Genetically engineered corn, soybeans, sugar beets and other crops are grown widely in the U.S. and used as oils, refined sugar, syrups, and grains in many food products.

Supporters of GMO labeling say foods made with GMO ingredients may be harmful to human health, and that consumers have the right to know what's in their food.

Opponents say that genetically modified crops are as safe as traditional crops, and that labeling would be unnecessary and costly for manufacturers, and misleading to consumers.

Similar mandatory labeling measures failed at the ballot box in Washington state last year, and in California in 2012. This summer, Vermont's governor signed the nation's first GMO labeling requirement into law, effective in 2016, but a group of grocery manufacturers, biotech firms and farmer groups have sued to block it.

Connecticut and Maine have also passed GMO labeling laws, but they won't take effect unless neighboring states pass similar legislation. Proposals to label genetically altered food have also been introduced in about 20 other states.