The US Department of Agriculture (USDA) is conducting an investigation at two further meat-packaging plants in its inquiry into the latest outbreak of Listeria.

USDA spokesman Steve Cohen said the organisation’s Food Safety and Inspection Service was carrying out investigations at at least two other establishments, although he declined to give further details.

Since July, the USDA has started investigating 120 cases of Listeria, 23 of which were fatal. The department is working with the Centers for Disease Control and Prevention.

So far Pilgrim’s Pride and Jack Lambersky Poultry have been linked to the Listeria outbreak. Cohen said that the two new plants had already been mentioned in relation to the case.

To see an earlier story on Jack Lambersky, which recalled 200,000 pounds of poultry last weekend, click here.