05/08/2015 03:20 EDT | Updated 05/07/2016 05:59 EDT

FDA says listeria contamination in Blue Bell plants goes back more than 2 years

WASHINGTON - A government investigation found Blue Bell Creameries knew there was listeria in one of the company's plants as far back as March 2013. But the company didn't issue any recalls or shut down production until after the products were linked to listeria illnesses this year — including three deaths in Kansas.

The Food and Drug Administration on Thursday released results of investigations into Blue Bell's plants in Oklahoma, Texas and Alabama. The most extensive violations were found in Oklahoma, where the FDA listed 17 positive tests for listeria on equipment and around its plant there from March 2013 through February 2015.

Neither Blue Bell nor the FDA has said why the Oklahoma plant was not closed after repeated findings of listeria, which was found in multiple locations around the plant.