The recall follows by days the decision by Safeway Inc., Pleasanton, Calif., to remove taco shells sold by Gruma from about 1,600 stores over concerns that the StarLink protein might be present in several shipments. Similar concerns caused Kraft Foods Inc., a division of Philip Morris Cos., to recall its taco shells from grocery stores last month.

Mission Foods Corp., Irving, Texas, the nation's leading manufacturer of tortillas, announced it was recalling all of its taco shells, tortilla chips, tortillas and other products milled from yellow corn. Mission's sistery company, Azteca Milling, announced a similar recall of yellow-corn flour, and its intention to switch to white corn while the StarLink probe continues.

"Because StarLink is a yellow corn, and we believe that we need to assure our customers and the public that products made with our flour are safe, the surest way to bolster confidence is to make products with only white corn," and Dan Lynn, Azteca Milling's president. Azteca Milling is a limited partnership between Gruma and ,b>Archer-Daniels-Midland Co.

Officials at Mission Foods' headquarters, as well as at Gruma's home office in Mexico, maintain that how the StarLink protein got into the corn remains a mystery. They say the problem seems to be confined to a single milling facility in Plainview, Texas, and that through last week, both Mission Foods and Azteca Milling were working with customers to ensure that all products derived from flour milled in Plainview were recalled and stockpiled.

Kraft Foods' Taco Bell, one of Mission's largest customers, directed its restaurants' taco shell manufacturers to switch their corn flour supply from Texas to mills in other parts of the country.

With other $600 million in annual sales north of the border, Gruma is one of Mexico's largest multinations. Its share of the U.S. tortilla market is estimated to run as high as 50%, according to analysts, making it the single largest player in the Mexican-food sector, the restaurant industry's fastest-growing. Gruma's largest U.S. rival in tortillas, Tyson Foods Inc., is a customer as well-competing with its Mission Foods to sell tortillas to Taco Bell and others, but also buying corn flour from Gruma's Azteca Milling subsidiary.