The seed of alfalfa hay rejected for export late last month contained low levels of the Roundup Ready genetic trait, Washington State Department of Agriculture (WSDA) officials said Friday.

An eastern Washington grower intended to grow conventional alfalfa, but the seed he purchased was mislabeled, state officials believe.

"It's not the seed he thought he was buying," says Mike Louisell, WSDA public information officer.

A broker rejected the hay in late August after it tested positive for genetically modified organisms (GMOs), and WSDA began tests last week, Louisell says. Tests of the seed detected low GMO levels. Plant material tested negative, although that test is less sensitive, he says.

WSDA testing does not give a percentage of the Roundup Ready trait.

Roundup Ready alfalfa, developed by Forage Genetics International for Monsanto Co., was deregulated by USDA in 2011, and many farmers have taken to the varieties that withstand Roundup herbicide.

WSDA is consulting with USDA to decide whether to take any further action.