Two elderly men died from listeriosis contracted from contaminated milk from Whittier Farms in Shrewsbury, Mass. in June and October. Just this week, state health officials warned consumers not to drink milk from the farm, while they investigated the source of contamination.

Officials today announced that the pasteurization process at the dairy was found to be working properly and that contamination must have occurred after the milk was pasteurized.

Doctor Alfred DeMaria, the state director of communicable disease control, says the dairy appeared to do everything right.

The dairy continues to suspend operations and work with officials to pinpoint the source of the deadly listeria.