By Mary Clare Jalonick, Associated Press

WASHINGTON (AP) — Consumers wanting to know if their foods contain genetically modified ingredients will be able to find out for the first time.

Congress sent legislation (pdf) to President Barack Obama on Thursday that would require most food packages to carry a text label, a symbol or an electronic code readable by smartphone that indicates whether the food contains genetically modified ingredients, or GMOs. The Agriculture Department would have two years to write the rules.

The White House says Obama will sign the bill, which would pre-empt a Vermont law that kicked in earlier this month. The House passed the legislation 306-117 on Thursday.

Senate approval came last week over the strong objections of Vermont's congressional delegation. Sens. Bernie Sanders and Patrick Leahy and Rep. Peter Welch argued that the measure falls short, especially compared with the tougher labeling requirements in their state. While the bill gives companies the three options for labeling, the Vermont law would require items be labeled "produced with genetic engineering."

"If there is an acknowledgement about the right of a consumer to have access to information, why not give them the information in plain and simple English?" asked Welch on the House floor.

Advocates for labeling and the food industry, which has fought mandatory labeling, have wanted to find a national solution to avoid a state-by-state patchwork of laws. The food industry supports the legislation, which was the result of bipartisan Senate negotiations. But many advocates do not, arguing that many consumers won't be able to read electronic labels and that there aren't enough penalties for companies that don't comply.

While there is little scientific concern about the safety of those GMOs on the market, advocates for labeling argue that not enough is known about their risks and people want to know what's in their food. Among supporters of labeling are many organic companies that are barred by law from using modified ingredients in their foods.

The food industry says GMOs are safe and the labels could mislead people into thinking they aren't. But several companies started to label their foods anyway as Vermont's law went into effect.

Vermont's Democratic Gov. Peter Shumlin bemoaned the congressional action.

"It's a shame that Congress chose to replace our standard with a weaker one that provides multiple ways for the food industry to avoid transparent labeling," he said in a statement.

Republicans and lawmakers from rural states overwhelmingly supported the legislation. Agriculture groups have backed it, hoping it will bring more certainty to farmers who grow genetically modified corn and soybeans.

"The clock has run out, my producers need certainty and an interstate commerce nightmare will shortly ensure if we don't pass this bill," said Rep. Rodney Davis, R-Ill.

Genetically modified foods are plants or animals that have had genes copied from other plants or animals inserted into their DNA. While farmers have been selectively breeding plants for centuries, this manipulation is done in a lab, speeding up the process by transferring a gene from one plant or animal to another. The engineering is done to create certain traits, like resistance to herbicides.

The bulk of the nation's genetically engineered crops are corn and soybeans that are eaten by livestock or made into popular processed food ingredients such as cornstarch, soybean oil or high-fructose corn syrup. Only a handful of genetically engineered fruits and vegetables are available in the produce aisle, including Hawaiian papaya, some zucchini and squash and some sweet corn.

The food industry says 75 percent to 80 percent of foods contain genetically modified ingredients — most of those corn and soy-based. The Food and Drug Administration says they are safe to eat.

The legislation encompasses some foods that were exempted from the Vermont law, but it also allows the Agriculture Department to determine how much of a "bioengineered substance" must be present to require a GMO label. Labeling advocates say many foods wouldn't be labeled if the department sets a high threshold.

Associated Press writer Matthew Daly in Washington and David Gram in Vermont contributed to this report.

To Learn More:

Vermont First State to Require GMO Food Labeling, But Preemptive Weaker Federal Bill Looms (by Dave Gram, Associated Press)

GMO Food Labeling Advocates Attack Bipartisan Senate Deal on Industry-Backed Labeling Rules (by Mary Clare Jalonick, Associated Press)

Senate Republicans Fail in Attempt to Block States from Requiring GMO Food Labeling (by Mary Clare Jalonick, Associated Press)

House Members who Voted to Stop States from Mandating GMO Labeling Received $30 Million from Agribusiness and Food Industries (by Steve Straehley, AllGov)

House Republicans Fast-Track Bill to Prevent States from Labeling GMO Foods (by Noel Brinkerhoff and Steve Straehley, AllGov)

Americans Overwhelmingly Want GMO Labeling…Until Big Companies Pour Money into Election Campaigns (by Noel Brinkerhoff, AllGov)