The Environmental Protection Agency has proposed more than doubling the number of states allowed to use a new version of a popular weed killer on genetically modified crops despite its earlier concerns.

Environmentalists are outraged with the proposal to increase from 15 to 34 the number of states that could use Enlist Duo, noting that the EPA sought court authority last year to withdraw approval of the weed killer.

The EPA had cited information from manufacturer Dow AgroSciences that indicated Enlist was probably more toxic to other plants than previously thought. But the agency said this week that its review determined Enlist "does not show any increased toxicity to plants and is therefore not of concern." Dow Chemical Company said in a statement Thursday that it was "pleased" with the proposal.

George Kimbrell, senior attorney with the Center for Food Safety, accused the EPA of "capitulation to the agrichemical industry."

The Washington-based advocacy group was among the environmental and food safety groups that sued to rescind approval of Enlist, which is a combination of glyphosate and an updated version of an older herbicide named 2,4-D. Enlist is aimed at use with seeds engineered to resist the herbicide, as farmers look for new options as many weeds become resistant to older pesticides.

Enlist is currently approved for use on soybeans and corn. The EPA proposal would also allow cotton.

The EPA is seeking comment through Dec. 1.