Test results linking two bags of Dole brand baby spinach to a deadly E. coli strain have helped health officials hone in on a specific batch from a San Juan Bautista processing plant that may be the source of a nationwide outbreak.

The investigation remains focused on Natural Selection Foods LLC, which officials believe packaged the tainted spinach for Dole and dozens of other brands. They're looking specifically at nine farms in three California counties that supplied the company with leafy greens.

Both tainted bags — one found in Utah over the weekend and the other in New Mexico earlier last week — were processed during the same shift on Aug. 15 at Natural Selection's plant, said Dr. Kevin Reilly, deputy director of prevention services for the California Department of Health Services.

"We are looking very aggressively at what was produced on that date," Reilly said Monday. "Much of the feedback we got from patients right now was related to Dole packaging."

Pennsylvania health officials said Tuesday a bag of Dole baby spinach purchased there was also tied to the deadly E. coli strain. A lab identified the strain in a sample of spinach purchased on or around Sept. 8 in western Pennsylvania.

About two dozen cases have yet to be confirmed as related to the spinach outbreak. West Virginia health officials said Tuesday they confirmed that a 71-year-old man there was sickened by the strain of E. coli linked to spinach.

"We probably are seeing the tail end of the outbreak," said Howard Backer, California's acting public health officer. "Partly as a result of spinach being taken off from the market, there is not ongoing contamination."

The E. coli outbreak from spinach has sickened at least 175 people, the U.S. Food and Drug Administration said Monday. More than half — 93 — were hospitalized, including a 77-year-old Wisconsin woman who died.

Two other deaths have been reported in suspected cases — a child in Idaho and an elderly woman in Maryland — but those cases still are being investigated.

In addition to Dole, Natural Selection Foods has recalled more than 30 brands, including President's Choice, Ready Pac, Trader Joe's, Nature's Basket and Premium Fresh.

It was too soon to say whether any other brands besides Dole would turn out to have been contaminated, he added. Calls to Dole's headquarters in Westlake Village were not returned Monday.

Although the FDA has recommended that people not eat fresh, raw spinach, it said Friday that spinach grown anywhere outside California's Salinas Valley is safe to eat.

Salinas Valley farmers and growers were developing new food safety guidelines they need to have approved by the FDA before the agency lifts its consumer warning on locally grown and packaged spinach.

"At this point, there is not a finalized proposal, but I know there is a lot of effort going forward with that right now," Reilly said Monday.

Over the weekend, two companies in the Pacific Northwest voluntarily recalled some of their products because they may contain spinach supplied by Natural Selection.

Seattle-based Triple B Corp. recalled salad products distributed to retail stores and delis in Washington, Oregon, Idaho and Montana that had "use by" dates of Aug. 22 through Sept. 20.

Pacific Coast Fruit Company, based in Portland, Ore., recalled salad and pizza that may have been made with spinach supplied by Natural Selections. The products were distributed in Alaska, Oregon, Washington and Idaho.

The 26 states that have reported E. coli infections since the spinach-linked outbreak was identified last month are Arizona, California, Colorado, Connecticut, Idaho, Illinois, Indiana, Kentucky, Maine, Maryland, Michigan, Minnesota, Nebraska, Nevada, New Mexico, New York, Ohio, Oregon, Pennsylvania, Tennessee, Utah, Virginia, Washington, West Virginia, Wisconsin and Wyoming.