Belgian supermarket chain Delhaize has recalled thousands of free-range eggs sold in its Belgian stores after tests showed possible contamination from cancer-causing chemicals.

Preliminary test results indicated the eggs contained between two-and-a-half and five times the normal level of PCBs, environmental contaminants that have been linked to cancer, reported the Independent.

Belgian food safety agency Afsca is trying to determine the cause of the contamination. PCBs are found in many foods in low concentrations and are not thought to be harmful to humans in small doses.