The U.S. Attorney's office for the Northern District of California has closed the investigation into the September 2006. E. coli O157:H7 outbreak in fresh spinach, says attorney Scott Schools.

The investigation included October 2006 searches oft Growers Express in Salinas, Calif., and Natural Selection Foods in San Juan Bautista, Calif., as well as a number of fields in Santa Clara, Monterey and San Benito counties.

In a press release, Schools says, "After a thorough and wide-ranging investigation, we have determined that federal criminal charges are not warranted in this matter. I thank both companies for their cooperation in this investigation."

On its Web site, Natural Selection Foods posted this comment:

"We believe that the decision of the U.S. attorney to close this investigation was the right move. Since the outbreak last year, Natural Selection Foods has led the industry in implementing the most aggressive food safety practices, as evidenced by our advanced testing procedures intended to detect pathogen contamination at every stage from seed to harvest, and through processing in our facilities. We will continue our commitment to be industry leaders in food safety and product quality."