Tens of thousands of people have marched through Mexico City to protest at the rising price of Tortillas.

Tortillas, the flat corn bread and staple diet item for many Mexicans, has risen in price by over 400%. Many people blame the rise in demand for corn on the bio-fuels market where corn is converted to ethanol and used as an environmentally-friendly fuel in the emerging US 'green' car market.

The 1994 North American Free Trade Agreement allowed Mexico to receive cheap corn imports from the United States, but the demand for bio-fuels has diverted corn sales to the more lucrative ethanol production market and thus corn supply to Mexico is reduced and corn prices are up accordingly.

Not surprisingly, the tens of thousands who demonstrated in Mexico City were angry about the soaring costs of tortillas as there is the possibility of malnourishment amongst the poorest people in Mexico.