By Carey Gillam and Lisa Baertlein

(Reuters) - The Vermont Senate passed a bill on Wednesday that would make it the first U.S. state to enact mandatory labeling of foods made with genetically modified organisms, or GMOs.

Unlike bills passed last year in Maine and Connecticut, which require other states to pass GMO labeling laws before they can be enacted, Vermont's contains no such trigger clause.

Vermont's effort comes as the developers of genetically modified crops and the $360 billion U.S. packaged food industry push for passage of an opposing bill introduced in Congress last week that would nullify any law that would require labeling of foods made with genetically modified crops.

GMO labeling is just one front in an increasingly high-stakes food fight raging in the United States, where consumers increasingly are demanding to know where their food comes from and how it was produced.

"We have a growing food movement in which people are demanding more transparency," said Michele Simon, a public health attorney and president of Eat Drink Politics.

When it comes to GMO labeling, "the issue is disclosure of a technology that people have real concerns about," Simon said.

Vermont's bill, approved 28-2 by the Senate, has already passed the state House of Representatives. It now goes back to the House to see whether members will approve changes made by the Senate. If passed, the law would take effect July 1, 2016.

"We are really excited that Vermont is going to be leading on this," said Falko Schilling, a spokesman for the Vermont Public Interest Research Group, which backed the bill.

According to the National Conference of State Legislatures, there are GMO labeling bills under consideration in 29 states.

GMOS EVERYWHERE

Products made with GMOs are ubiquitous in the aisles of many U.S. supermarkets.

Some of the most popular U.S. GMO crops are corn, soybeans and canola, which are staple ingredients in virtually every type of packaged food, from soup and tofu to breakfast cereals and chips. Organic foods do not contain GMOs.

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The Vermont bill passed by the Senate would require GMO-containing foods sold at retail outlets to be labeled as having been produced or partially produced with "genetic engineering."

Andrea Stander, a spokeswoman for the Vermont Right to Know GMOs coalition, said they expect the biotech industry to sue in an attempt to stop enactment of the bill. As such, the language of the bill includes formation of a fund that would pay legal bills.

Consumer groups say labeling is needed because of questions both about the safety of GM crops for human health and the environment.

The language of the Vermont bill states that foods made with genetically engineered crops "potentially pose risks to health, safety, agriculture and the environment", and should be labeled.

Last October, a group of 93 international scientists issued a statement saying there was a lack of empirical and scientific evidence to support what they said were false claims the biotech industry was making about a "consensus" on safety.

The group said there needed to be more independent research as studies showing safety tend to be funded and backed by the biotech industry.

But GMO crop developers such as Monsanto, and their backers say genetically modified crops, also referred to as biotech crops, have been proven to be safe.

"This debate isn't about food safety," said Karen Batra, spokeswoman for the Biotechnoloy Industry Organization. "Our science experts ... point to more than 1,700 credible peer-reviewed studies that find no legitimate concern."

Batra said mandatory labeling creates needless extra costs and complications for farmers and the food industry.

A Monsanto representative did not immediately respond to requests for comment.

Ballot measures in California in 2012 and last year in Washington state were narrowly defeated after well-funded opponents poured millions into campaigns to defeat the measures. The opposition included Monsanto, the world's largest seed company and the first to introduce genetically engineered products, other biotech crop developers and members of the Grocery Manufacturers Association, an industry group representing packaged food makers.

The Vermont bill also would make it illegal to describe any food product containing GMOs as "natural" or "all natural."

(Editing by Bernadette Baum and Ken Wills)