According to the FDA inspection report from its investigation following the listeria outbreak, surfaces at Blue Bell's plant in Broken Arrow, Oklahoma, tested positive for listeria five times in 2013, 10 times in 2014 and once in January 2015. The surfaces included the floor in front of a freezer, the drain behind a flavor tank and, the report notes, something at a "half gallon filler" tested positive, but the identifying information of this item was redacted in the report.
"Specifically you failed to demonstrate your cleaning and sanitizing program is effective in controlling recurring microbiological contaminations," the FDA report says.
Blue Bell said it was using tests for listeria and other microbials to determine whether cleaning and sanitation was effective, the report says, but despite the positive listeria tests, the ice cream company didn't make any adjustments.
Food safety attorney Bill Marler said the inspection reports released today are among the worst he's seen in his 20-year career.
"How Blue Bell could run a plant with years of positive listeria test results is shameful," he said.
Marler said he is representing two listeria-positive Blue Bell victims.
Blue Bell spokesman Joe Robertson gave the following statement to ABC News:
"Several swab tests did show the presence of listeria on non-food surfaces in Blue Bell's Broken Arrow plant in 2013. As is standard procedure for any such positive results, the company would immediately clean the surfaces and swab until the tests were negative. We thought our cleaning process took care of any problems, but in hindsight, it was not adequate, which is why we are currently conducting such a comprehensive re-evaluation of all our operations."
ABC News' Gitika Kaul contributed to this report.