WASHINGTON — It’s O.K. to eat romaine lettuce again, federal health officials said on Monday — as long as you’re sure it wasn’t grown on California’s north and central coast.

The Food and Drug Administration and the Centers for Disease Control and Prevention said investigators had traced the romaine lettuce associated with an outbreak of E. coli that has sickened 65 people in 12 states and Canada to “end of summer” romaine lettuce harvested from that region.

With the growing and harvesting season over there, according to the F.D.A., people may eat romaine lettuce that has been hydroponically or greenhouse grown, or has been harvested from the winter growing desert regions of the United States, and is labeled such.

“If it does not have this information,” the agency said in a statement posted on its website, “you should not eat or use it.”