BELGRADE — Serbian officials ordered some brands of milk taken off store shelves on Wednesday despite earlier assertions that they were safe and not dangerously contaminated with a potentially cancer-causing toxin.

The order came after widespread public outrage over allegations that health authorities have for weeks been hiding the results of lab tests that reportedly show that much of the milk sold in Serbia contains high levels of aflatoxins, a fungus linked to mildewed cattle feed that can cause cancer if consumed in high doses.