Records show that Blue Bell was aware of a contamination at one plant since 2013, CBS reports. The Department of Justice is now trying to determine what management knew about the contamination and when they knew it.

The company’s three factories halted production in April when its ice cream was linked to 10 listeria cases. At the time, Blue Bell products were immediately pulled from stores. They’re already on sale in some locations and are slated to be sold in more states next month.

Ricky Dickson, Blue Bell’s vice president of sales and marketing, announced in August that the ice cream would gradually be returning to shelves. Soon after, two former factory workers told CBS in an interview about unsanitary conditions. “On the wall by the 3-gallon machine, if it had rained real hard and water sat on the roof, it would just trickle down,” said ex-employee Gerald Bland in an interview with CBS.

Terry Schultz, another employee, recalled attempting to tell Blue Bell management about the situation. The response he reportedly received: “Is that all you’re going to do is come here and bitch every afternoon?” An investigation by the FDA found unclean factory equipment and condensation falling directly into the products.

Blue Bell could not immediately be reached for comment.