WASHINGTON (AP) — Major recalls from two well-known ice cream companies due to the discovery of listeria bacteria raise questions about how the pathogen could have contaminated multiple ice cream manufacturing plants — and whether the discoveries are related.

Blue Bell Creameries of Texas and Jeni’s Splendid Ice Creams of Ohio both took products off shelves this week after listeria was discovered in their products. Blue Bell ice cream is linked to 10 illnesses in four states, including three deaths. There are no known illnesses linked to the Jeni’s recall.

The recalls are unusual: Listeria is rarely found in ice cream because it can’t grow at freezing temperatures. A spokesman for the Food and Drug Administration says it has no evidence, for now, that the two recalls are connected.