TIJUANA, Mexico (AP) _ In apparent violation of the North American Free Trade Agreement, American milk is being pulled off Tijuana grocery shelves.

Supermarkets in the border city began stocking American milk earlier this month, for the first time in recent memory.

But the plastic jugs were yanked soon after, banned by Baja California state officials who say they're trying to protect their state's crucial dairy industry.

The move to restrict U.S. milk appears to violate NAFTA, which eliminated import quotas, a U.S. Department of Agriculture official told the San Diego Union-Tribune newspaper.

Although NAFTA allows the exclusion of agricultural products under health regulations, restrictions to protect a domestic industry are not within its provisions, the official told the paper, speaking on condition of anonymity.

The official said Washington has not taken any action in this case and he was not sure whether it would.

The free trade agreement among the United States, Mexico and Canada went into effect Jan. 1, creating the world's largest free trade zone.

The gallons of whole milk from a Yuma, Ariz., dairy, marketed under the name Sarah Farms, first popped up May 9 in the Calimax chain's 18 Tijuana stores. The jugs sold for $2.34, slightly more than the $2.18 per gallon charged for milk from the Jersey dairy in Tijuana.

Calimax was told it had committed a technical violation by not obtaining a state permit for the milk, but state officials concede they are reluctant to grant the permit.

''The state government is very concerned about protecting the jobs and the economic benefits that the milk industry generates,'' said Jose Manuel Salcedo Sanudo, undersecretary in Baja California's department of agricultural development.

Milk producers in Baja California say 120,000 people are employed in the state's dairy industry, either growing alfalfa for cows, raising cows or processing milk.

The United States exports milk to all Mexican border states, including Baja California, but no one had tried to break into the Tijuana market before.

Tijuana is the biggest Mexican city along the U.S. border, and the import of American milk for Tijuana consumers could seriously hurt domestic milk producers.