OMAHA — A lawsuit was filed Tuesday on behalf of the estate of a Nebraska woman who health officials say died because she was infected with E. coli after eating fresh spinach.

The lawsuit, filed after Ruby Trautz, 81, of Bellevue, died in August, names “John Doe Farms,” Dole Food Co., Natural Selection Foods and No Frills Supermarkets as defendants.

“This far into the outbreak investigation, FDA should have already named the farm where the spinach came from,” attorney Bill Marler said in a release Tuesday. “We included John Doe Farms as a defendant to try to get more answers for our clients.”

The lawsuit was filed in Sarpy County District Court.

Trautz was one of three people known to have died in the nationwide outbreak, according to health officials.

Investigators are still trying to pinpoint the source of the bacteria.

E. coli lives in the intestines of cattle and other animals and typically is linked to contamination by fecal material. It causes an estimated 73,000 infections in the United States each year, including 61 deaths, according to the CDC.

Sources can include uncooked produce, raw milk, unpasteurized juice, contaminated water and meat, the agency said.

A representative for the Dole Co. referred a telephone call from The Associated Press to Marty Schenker, a lawyer for Natural Selection Foods. Schenker said he did not represent Natural Selection Foods in personal-injury cases.

Telephone calls to Natural Selection Foods and No Frills Supermarkets seeking comment were not immediately returned.