Thousands of protesters blocked major avenues in Mexico City, Wednesday, and clashed with police before moving peacefully to the city's central plaza to establish a camp. The protesters are upset about plans to locate a new airport on their land.

In a clash on one city street, demonstrators threw rocks and attacked Mexico City riot police with machetes. Police responded with their batons and detained seven people. At least five protesters and two policemen were injured in the clash.

Mexico City Security Chief Leonel Godoy says his forces tried to avoid conflict. He says "it is unfortunate that this violence occurred because the protest has nothing to do with Mexico City." Godoy says "his police were only trying to keep the protesters from blocking city streets."

The demonstration was directed at Mexico's federal government and President Vicente Fox. It was a protest against Mr. Fox's recent decision to locate Mexico City's new airport in the community of Texcoco. The people living in Texcoco, 23 kilometers east of Mexico City, are solidly against the plan. Most of them are farmers who say the government is expropriating land they have had in their families for generations and offering them about what it would cost to buy a soft drink for each square meter.

The people of Texcoco have found support from various sectors of Mexican society, including environmentalists, who say the construction of the airport there would have a negative impact on migrating birds. They also object because of damage to water resources in the area and the air pollution that would result from the planes and traffic around the airport.

The Fox government says the new airport is needed because the current airport cannot be expanded. Government officials say the Texcoco site is the most cost effective and that its location also makes it desirable. The other site that was under consideration, in Hidalgo State, is 80 kilometers north of the city. The process of selecting a new airport site took 30 years and, even if the expropriation of land in Texcoco proceeds, construction on the site is not expected to begin for another few years.