A third bag of Dole baby spinach that tested positive for a deadly E. coli strain has been linked to a specific batch packaged at a Salinas Valley plant, state health officials said.

A Pennsylvania state lab identified the strain Tuesday in a sample of spinach purchased on or around Sept. 8 in Indiana County. Samples from the individual who was believed to be sickened by eating the spinach still are being tested.

At least 183 people nationwide have been sickened by eating spinach tainted by the same E. coli strain.

The Pennsylvania package was processed on Aug. 15 at San Juan Bautista-based Natural Selection Foods LLC, the same date and place as bags of Dole spinach found last week in New Mexico and Utah, a California Department of Health Services officials said.

"Some contamination entered the facility on that date," said Jeffrey Farrar, chief of the food and drug branch.

The federal and state investigation to find the source of the E. Coli remains focused on Natural Selection Foods, which packaged spinach for Dole and dozens of other brands. The company could have processed tainted spinach on other dates, Farrar said.

Inspectors also are looking at nine farms in Monterey, Santa Clara and San Benito counties that supplied Natural Selection with fresh spinach.