The warning is no longer in effect as the contaminated lettuce from the Yuma, Arizona, growing region is no longer harvested. Three more states have reported ill people - Arkansas, North Carolina and Oklahoma.
Nationally, five people have died from E. coli poisoning from the tainted leafy greens; no deaths have been recorded in Texas.
According to the latest CDC update, there have been a total of 197 illnesses, 89 hospitalizations and five deaths in 35 states. Canadian health officials also recently identified E. coli cases in several provinces that could potentially be linked to the outbreak in the United States.
Two deaths from the current outbreak occurred in Minnesota, and one each in Arkansas, California, and NY.
The outbreak was first reported on March 13, reports CNN.
The growing season there ended six weeks ago, and it's unlikely any tainted lettuce is still in stores or people's homes, given its short shelf life. Symptoms can include bloody diarrhea, vomiting and severe stomach cramps.
Almost half of those who became ill had to be hospitalized.
"We are actively evaluating a number of theories about how romaine lettuce grown on multiple farms in the same growing region could have become contaminated around the same time", Dr. Scott Gottlieb and Dr. Stephen Ostroff wrote.
Most E. coli bacteria are not harmful, but some produce toxins that can cause severe illness. Almost half of those who got sick have been hospitalized, and 26 developed a type of kidney failure called hemolytic uremic syndrome.
"Some people who became sick did not report eating romaine lettuce, but had close contact with someone else who got sick from eating romaine lettuce".