BANGALORE, India (AP) _ Police arrested 29 farmers on riot charges Thursday after a group injured two workers and destroyed a greenhouse at a research facility belonging to U.S.-based Monsanto Co., which sells genetically modified seeds.

The farmers threw stones and stormed buildings on the campus of the Indian Institute of Science in this southern Indian city, police said.

Two Monsanto workers were injured, said Ranjana Smetacek, a spokeswoman for Monsanto India.

``We had our research facility at the campus ransacked today,'' Smetacek said. ``One greenhouse, where we grow plants for research, was destroyed.

``We have lost valuable plants and the result of lot of work by our researchers. Now we will have to redo all that,'' she said.

The protesters said genetically modified seeds were environmentally hazardous and could contaminate the genes of natural crops through cross pollination.

``We timed the attack to draw the attention of those attending the World Trade Organization meeting in Cancun, Mexico,'' said M.D. Nanjundaswamy, president of the Karnataka State Farmers Association.

The Monsanto spokeswoman said, ``We are seriously concerned by today's attack. As an investor, we want the government to ensure the safety of our facilities and our people.''

The Maharashtra Hybrid Seeds Company, Monsanto's joint venture partner in India, has sold more than 230,000 packets of 450-gram BT cotton packets in six Indian states during a recent planting season. BT stands for bacillus thuringiensis, a bacterium whose gene is injected into cotton seeds to make them pest-resistant.

Monsanto is the only company allowed to sell such seeds in India.

The sale of genetically modified cotton is allowed in six of India's 29 states. Sales this season were 216 percent higher than in 2002, the first year of genetically modified crop sales in India.

In trading on the New York Stock Exchange, Monsanto shares rose 4 cents to $25.05.