LOS ANGELES, Aug 28 (Reuters) - Rice farmers in Arkansas, Missouri, Mississippi, Louisiana, Texas and California have sued Bayer CropScience, alleging its genetically modified rice has contaminated the crop, attorneys for the farmers said on Monday.

The lawsuit was filed on Monday in the U.S. District Court for the Eastern District of Arkansas in Little Rock, law firm Cohen, Milstein, Hausfeld & Toll said in a statement.

The farmers alleged that the unit of Germany's Bayer AG <BAYG.DE> failed to prevent its genetically modified rice, which has not been approved for human consumption, from entering the food chain.

As a result, they said, Japan and the European Union have placed strict limits on U.S. rice imports and U.S. rice prices have dropped dramatically.

A Bayer representative could not be immediately reached for comment.

U.S. agriculture and food safety authorities learned on July 31 that Bayer's unapproved rice had been found in commercial bins in Arkansas and Missouri. While the United States is a small rice grower, it is one of the world's largest exporters, sending half of its crop to foreign buyers.

The genetically engineered long grain rice has a protein known as Liberty Link, which allows the crop to withstand applications of an herbicide used to kill weeds.

The European Commission said on Wednesday the EU would require U.S. long grain rice imports to be certified as free from the unauthorized strain. The commission said validated tests must be done by an accredited laboratory and be accompanied by a certificate.

Japan, the largest importer of U.S. rice, suspended imports of U.S. long-grain rice a week ago.

The U.S. Department of Agriculture and Food and Drug Administration have said there are no public health or environmental risks associated with the genetically engineered rice.

The United States is expected to produce a rice crop valued at $1.88 billion in 2006. U.S. rice growers are responsible for about 12 percent of world rice trade. Three-fourths of the crop is long grain, grown almost entirely in the lower Mississippi Valley. California, the No. 2 rice state, grows short grain rice. (Additional reporting by Christopher Doering in Washington)