In the wake of a national recall of frozen hamburger patties contaminated with the deadly germ E. coli, Maine health officials are investigating a cluster of illnesses that may be related to the tainted meat.

On Tuesday, the Topps Meat Co. of Elizabeth, N.J., issued a recall of about 331,582 pounds of frozen beef patties and 21 products that were distributed nationwide after public health investigators linked the ground beef to a number of E. coli cases in the northeastern United States. As of Thursday, 23 people in eight states, including Maine, had fallen ill, though it was still unclear how many of those cases were directly linked to the contaminated hamburger.

E. coli is a potentially lethal organism that can cause bloody diarrhea and dehydration. The very young, the elderly and people with compromised immune systems are most likely to become seriously ill from consuming contaminated foods.

Nationwide, no one has died but some victims have required hospitalization.

There has been “a general increase” in cases of E. coli in Maine over the past three or four weeks, according to Dr. Dora Anne Mills, director of the Maine Center for Disease Control and Prevention. In a health alert issued Sept. 19, the Maine CDC announced it was investigating six cases of E. coli in midcoast and central Maine. Since then, Mills said Thursday, a handful of additional cases have been identified in a geographic band stretching across the state from the midcoast area to the Farmington area.

Mills said one of the original six cases has been definitively linked through laboratory testing to the batch of contaminated beef. The affected individual lives in Franklin County, she said, and is expected to recover fully. Another of the original cases has been determined to be unrelated to the beef shipment, she said, and results of all other cases are still incomplete. No one in Maine has developed life-threatening symptoms or has required hospitalization, Mills said.

Though wholesale food distributors are responsible for getting the word out to their customers, public inspectors are scouring major grocery outlets for the contaminated beef, according to Hal Prince of the state Department of Agriculture.

Prince said Thursday that Shaw’s, Hannaford and Wal-Mart are among the stores known to have received some of the contaminated batch of burgers, but convenience stores and other retail outlets also should check their shelves.

“We’ll be on the lookout for a long time,” he said. Federal inspectors from the U.S. Department of Agriculture also are responding in Maine, he said.

Federal food inspectors meanwhile continued to investigate the Topps facility and its suppliers. USDA is looking into what controls the Elizabeth-based company has in place to protect against E. coli, agency spokeswoman Amanda Eamich said.

Topps Meat Co., the leading U.S. manufacturer of frozen hamburgers, said this was its first recall in its 65-year history.

Mills at the Maine CDC said distributors and restaurants work together to ensure recalled products don’t make it onto diners’ tables. Even so, she said, consumers should be careful about the meat they order.

“All meat should be cooked to a minimum of 160 degrees,” she said. When she eats out, she said, she always orders her meat “well done” and slices into the middle of it before eating to be sure it looks safe.

“There should be no pink at all and the juices should be clear,” she advised.

More information about the recall, including a complete product list with photographs of packaging and labels, is available online at www.fsis.usda.gov/News&Events/Recall0402007Release/index.asp.