The Mexican branch of Monsanto Co., the world's biggest biotech seed company, planted genetically altered cotton on several plots of land in northern Mexico without authorization, the Environment Secretariat announced Wednesday.

In a news release, the Environment Secretariat said the company could face fines for realizing "activities with genetically modified organisms without getting permits and the respective authorizations."

The Environment Secretariat said it would solicit the intervention of the Agricultural Secretariat, which can impose administrative sanctions.

The Mexican branch of the St. Louis-based Monsanto planted the cotton seeds in an area covering about 100 hectares (247 acres) in the northern state of Sonora , the release stated.

The government said Monsanto had permits to plant genetically modified seeds in others areas of Sonora.

Monsanto officials could not be reached immediately reached for comment.

Genetically modified cotton has been altered to add beneficial traits such as resistance to insects and [resistance to] weed-killing chemicals.

Critics of such plants worry about risks such as the development of "superweeds" impervious to herbicides.