Mexico City ? President Felipe Calderon signed an accord with businesses on Thursday to curb soaring tortilla prices and protect Mexico’s poor from speculative sellers and a surge in the cost of corn driven by the U.S. ethanol industry.

The corn tortilla is the basic staple of the Mexican diet and is especially crucial for the poor.

The accord limits tortilla prices to 8.50 pesos ($0.78) per kilogram and threatens to use existing laws to achieve prison sentences of up to 10 years for company officials found hoarding corn. Some stores have been selling tortillas for as much as 10 pesos ($0.91) per kilogram.

It also raises quotas for duty-free corn imports to 750,000 metric tons (826,733 U.S. tons), most of which will come from the United States.

The measure is to be reviewed for possible modifications on April 30.

Tortilla prices rose by 14 percent in 2006, more than three times the inflation rate, and they have continued to surge in the first weeks of 2007.