The U.S. Centers for Disease Control and Prevention (CDC) expanded its warning about an E. coli outbreak found in romaine lettuce. The government is now saying that all romaine — not just the chopped forms found in salad mixes — can be contaminated, and washing the romaine won’t help.

The CDC was able to trace the outbreak to chopped romaine lettuce grown near Yuma, Arizona. However, on Friday, the agency announced that the head and hearts of the romaine could also be contaminated. Seeing as many package labels do not identify growing regions, the CDC now recommends disposing of any and all romaine in your fridge.

The E. coli outbreak has already affected 53 people across 16 states. While no one has died, 31 people have been hospitalized and five people have reportedly developed a type of kidney failure called hemolytic uremic syndrome. This expanded warning means that people can no longer avoid this strain of E. coli simply by washing the romaine. While that can sometimes do the trick if the bacteria is on the lettuce portion, CDC officials say that the E. coli bacteria are going much deeper than that.

“This bacteria can actually get inside the lettuce leaf,” Ian Williams, chief of the CDC’s Outbreak Response and Prevention Branch, told CNN. “Washing it doesn’t make it safe.” The CDC isn’t playing around. The agency warns that if you aren’t sure what type of lettuce it is, don’t risk it. Throw it out.

Infections from these bacteria usually take three to four days to develop, so more cases could appear. Williams asks anyone who has consumed romaine to be on the lookout for symptoms in the coming days, which stomach cramps, vomiting, and, “bloody diarrhea.” Anyone with these symptoms should see a doctor immediately and report the infection to local health departments. The CDC is already seeing varying levels of severity, with more than half of the known infections requiring hospitalization.

E. coli outbreaks aren’t rare and while most strains are considered harmless, the CDC’s updated warning suggests a more aggressive outbreak than initially believed. The agency has yet to identify a single grower, distributor, or brand involved in the outbreak, so it’s best to dispose of any store-bought romaine without question.