Consumers who purchased raw milk from Greenfield Dairy, 1450 Tittle Road, Middleburg, should discard it immediately due to possible Listeria monocytogenes contamination.

The Pennsylvania Department of Agriculture today said raw milk collected during required routine sampling by a commercial laboratory on April 8 tested positive for the bacteria.

Greenfield Dairy owned by Paul Weaver, sells directly to consumers at an on-farm retail store. The packaged raw milk is sold under the Greenfield Dairy label in half gallon glass containers dated April 18, 21, 22 and 24. It is labeled as “raw milk.”

Agriculture officials have ordered the owner of the dairy to stop the sale of all raw milk until further notice. Two samples taken at least 24 hours apart must test negative before the farm can resume raw milk sales.

Raw milk is milk that has not been pasteurized.

Pennsylvania law allows farms to sell raw milk but requires the farms to be permitted and inspected by the agriculture department to reduce health risks associated with unpasteurized products. There are 175 farms in Pennsylvania permitted to sell raw milk or raw milk cheese.