WASHINGTON — A food company is recalling lettuce sold in 23 states including Pennsylvania and the District of Columbia because of an E. coli outbreak that has sickened at least 19 people, three of them with life-threatening symptoms.

The Food and Drug Administration said Thursday that 12 people had been hospitalized and the federal Centers for Disease Control and Prevention said it was looking at 10 other cases probably linked to the outbreak.

Freshway Foods of Sidney, Ohio, said it was recalling romaine lettuce sold under the Freshway and Imperial Sysco brands because of a possible link to the E. coli outbreak.

College students at the University of Michigan in Ann Arbor, Ohio State in Columbus and Daemen College in Amherst, N.Y., are among those affected, according to local health departments in those states.

The FDA is focusing its investigation on lettuce grown in Arizona as a possible source for the outbreak, according to two people who have been briefed by the agency.

E. coli infection can cause mild diarrhea or more severe complications, including kidney damage.