BRENHAM, Texas (CNN) — After weeks of gradual recalls, Blue Bell Creameries is now pulling all of its products off the shelves.

The company is recalling its ice cream, frozen yogurt, sherbet and other frozen treats because they could be contaminated with Listeria monocytogenes, the company said Monday.

Three people have died and five others have fallen ill from the bacteria that may have come from Blue Bell products, health officials have said.

Blue Bell's decision to yank all its products came after tests showed some half-gallon containers of chocolate chip cookie dough ice cream contained listeria.

"This means Blue Bell has now had several positive tests for Listeria in different places and plants," the company said in a written statement.

"At this point, we cannot say with certainty how Listeria was introduced to our facilities, and so we have taken this unprecedented step."

The outbreaks

So far, Blue Bell has documented five cases of listeriosis in Kansas and three cases in Texas.

The Kansas Department of Health and Environment said three people in the state have died from listeria there over the past year, possibly due to Blue Bell products.

All five of the people who got sick in Kansas were patients being treated at the same hospital for unrelated causes, state health officials said.

Four of them drank milkshakes at the hospital made with Blue Bell ice cream, the Centers for Disease Control and Prevention said. It's not clear whether the fifth patient at the Kansas hospital had also consumed Blue Bell ice cream.

In a separate outbreak in Texas, three patients were infected with listeria between 2011 and 2014. Tests of those listeria strains "were nearly identical to Listeria strains isolated from ice cream produced at the Blue Bell Creameries' Oklahoma facility," the CDC said.

In March, Blue Bell recalled 3-ounce cups of chocolate, vanilla and strawberry ice cream after a test found listeria in one of the cups in Kansas.

Earlier this month, the recall expanded to some pints and half-gallon sizes of ice cream.

The symptoms

Listeria monocytogenes can cause serious and sometimes fatal infections in young children, frail or elderly people and others with weakened immune systems, the Food and Drug Administration says.

In the United States, an estimated 1,600 people become seriously ill with listeria each year; about 16 percent of these cases result in death.

Related:

Blue Bell working to get past listeria contamination scare

Blue Bell Creameries will survive the crisis caused by a recent recall of products prompted by a finding of bacterial contamination in some of its products, but it will take a lot of work and a lot of money, experts said.

Although some people might suffer only short-term symptoms such as high fever, severe headache, nausea, abdominal pain and diarrhea, listeria can also cause miscarriages and stillbirths.

The promise

Blue Bell CEO and President Paul Kruse promised to make sure all products are safe before they go back on sale.

"We're committed to doing the 100 percent right thing, and the best way to do that is to take all of our products off the market until we can be confident that they are all safe," Kruse said in a statement on the company's website.

"We are heartbroken about this situation and apologize to all of our loyal Blue Bell fans and customers."

Blue Bell said its new safety measures will include more extensive cleaning and sanitizing of equipment; increasing the swabbing and testing of facility surfaces by 800 percent; providing more employee training; and sending samples to a lab for testing every day.

— CNN's Catherine E. Shoichet, Ben Brumfield and Jeremy Grisham contributed to this report.

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