Federal health officials late Monday warned people not to eat certain Hello Fresh subscription meal kits containing spinach that may be contaminated with listeria.

The U.S. Agriculture Department issued a public health alert for the meals, which were produced by FreshRealm, the San Clemente, California-based company linked to an expanding listeria outbreak tied to heat-and-eat pasta meals.

The products include 10.1-ounce containers of Hello Fresh Ready Made Meals Cheesy Pulled Pork Pepper Pasta and 10-ounce containers of Hello Fresh Ready Made Meals Unstuffed Peppers with Ground Turkey. Both were shipped directly to consumers.

The pork pepper pasta is identified with establishment number Est. 47718 and lot code 49107 or Est. 2937 and lot code 48840. The unstuffed peppers with ground turkey is identified with Est. P-47718 and lot codes 50069, 50073 or 50698.

The problem was discovered when FreshRealm notified the USDA’s Food Safety and Inspection Service that the spinach used in the products tested positive for listeria bacteria.

Last month, FreshRealm said that tests confirmed that pasta used in linguine dishes sold at Walmart contained the same strain of listeria linked to an outbreak in June. That outbreak, originally tied to chicken fettucine Alfredo, has killed at least four people and sickened 20, with the most recent illness reported Sept. 11.

FreshRealm officials said genetic testing found the outbreak strain of listeria in samples of pasta made and supplied by Nate’s Fine Foods of Roseville, California.

Several additional companies including Kroger, Giant Eagle and Albertson’s have recalled pasta salads and other dishes made with products from Nate’s Fine Foods for potential listeria contamination.

Listeria infections can cause serious illness, particularly in older adults, people with weakened immune systems and those who are pregnant or their newborns. Symptoms include fever, muscle aches, headache, stiff neck, confusion, loss of balance and convulsions.

About 1,600 people get sick each year from listeria infections and about 260 die, the CDC says. Federal officials in December said they were revamping protocols to prevent listeria infections after several high-profile outbreaks, including one linked to Boar’s Head deli meats that led to 10 deaths and more than 60 illnesses last year.