In addition, the FDA inspects only about 1 per cent of the imports that fall under its jurisdiction. So the agency may miss many of the products that are contaminated or defective. The FDA database also fails to disclose the quantity of products that are refused, so it is impossible to know whether just a box of cucumbers was refused or a shipload.

In cases of recurrent problems, the FDA may issue an import alert, which leads to additional scrutiny at the border. Last month, for instance, the FDA issued not only the import alert for the Chinese fish, but also import alerts for Mexican cantaloupes and basmati rice from India, among others.

Rafael Laveaga, a spokesman for the Mexican Embassy in Washington, said the number of food safety problems from Mexican imports was minuscule given the huge volume of trade. He said that Mexican products were more scrutinised since they arrived by road transit.

Banarshi Harrison, minister of commerce at the embassy of India, said India had strengthened its food safety laws. He said contamination of spices and pickles might occur on occasion because they were processed by many small manufacturers. “There is no evidence of a systematic problem for any particular product,” he said.