The Food and Drug Administration is banning imports of milk and fresh fruit and vegetables from areas near the Fukushima Daiichi nuclear plant that was damaged by the March 11 earthquake and tsunami.

The FDA issued an import alert late Tuesday, allowing the agency to detain certain food at the border. The Japanese Ministry of Health Labour and Welfare has confirmed the presence of radioactive iodine in dairy, fresh produce and infant formula from areas around the nuclear power plant.

Specifically, the import alert affects dairy and produce products from the four Japanese prefectures of Fukushima, Ibaraki, Tochigi and Gunma. The FDA said it would continue to flag all food entries from Japan in order to determine whether they originated from the affected area, and will test food and feed shipments from the affected area for radiation contamination.

The FDA said foods imported from Japan constitute less than 4% of foods imported into the U.S., with dairy products representing an even smaller fraction. Most dairy products in the U.S. market are produced domestically.

The Japanese government has already ordered a stop to the sale of raw milk, spinach and kakina from the affected areas.