Eighteen people from five states have been added to the CDC’s romaine lettuce investigation since the agency first alerted the public to the E. coli outbreak on Friday, bringing the total to 53 people sickened in 16 states. The E. coli outbreak has led to 31 hospitalizations, according to the CDC, but no deaths have been reported.

Chopped romaine lettuce from the Yuma, Ariz., growing region appears to be responsible for the illnesses, according to the CDC. No single brand, grower, or distributor of the lettuce has been implicated in the E. coli outbreak, so the CDC is warning consumers to dispose of any store-bought romaine lettuce and avoid eating or buying more, unless it’s possible to confirm that the lettuce was not grown in the Yuma area.

Individuals who eat food or drink water that has been contaminated by E. coli bacteria may experience gastrointestinal issues. Most people recover within a week, according to the CDC, but in some cases, the E. coli infection can cause complications including a type of kidney failure called hemolytic uremic syndrome. Five individuals sickened by the current E. coli outbreak have developed this condition, the CDC says.

Symptoms of E. coli infection typically appear between two and eight days after exposure to the bacteria. All of the people currently included in the CDC’s investigation became ill between March 13 and April 6, but since there’s typically a lag between developing the illness and reporting it to health officials, the CDC says more cases may still be added to the list.