The source of the E. coli outbreak that has sickened people in Canada and across the U.S. is “likely” from romaine lettuce grown in California, according to the U.S. Food and Drug Administration.

In a tweet Friday, Scott Gottlieb, the commission of the FDA, said the current outbreak likely came from California based on “growing and harvesting patterns.” He said the government agency’s goal is to withdraw the product at risk of contamination from market and then “re-stock” the market.

There has been one case of E. coli in New Brunswick, three in Ontario, and 15 in Quebec. In the U.S., there have been at least 32 reported illnesses across 11 states related to the outbreak.

In a follow-up tweet, Gottlieb said the FDA is working with growers and distributers on labelling produce with location and harvest dates in order to keep track of it and to inform consumers the product is being sold “post purge.”

“We want to help unaffected growers get back into production and enable stores and consumers to re-stock,” he wrote.

On Friday, the U.S. Centers for Disease Control and Prevention (CDC) reiterated its advice to all consumers to throw out all romaine lettuce “regardless of brand, type, or if it is in a mixture.”

The agency also said its investigators are working with federal regulatory partners to determine the source of contamination.