The source of the E. coli contamination that has sickened at least 27 people in 15 states, and led to the recall of 10 million pounds of frozen food made by Rich Products Corp. at a plant in Georgia, remains a mystery.

The Buffalo-based manufacturer said it didn’t find any trace of E. coli after scouring the plant at the heart of the recall, and it now is investigating the plant’s suppliers as a possible source of the outbreak, which has led to the largest recall in Rich Products history.

“We’re looking at every possibility,” said Dwight Gram, a company spokesman.

The frozen pizza, quesadillas, mozzarella bites and other snacks made at the Waycross, Ga., plant under the Farm Rich brand were sold nationwide at retail stores, supermarkets and – through distributors – to customers that include eight area school districts and Catholic schools.

However, all of the illnesses reported by the federal Centers for Disease Control and Prevention were linked to E. coli-tainted food purchased at retail locations. No one has reported getting sick from food eaten in a school cafeteria.

The number of cases of E. coli infection could rise when the CDC provides an update later this week, and at least two area residents have reported getting sick after eating the recalled food.

The more seriously ill of the two, a Town of Tonawanda teenager, remains on dialysis at Veterans Affairs Medical Center in Buffalo for treatment of damage to his kidneys.

“He was very, very sick, and he continues to be very sick,” said Jed Dietrich, a lawyer retained by the teen’s family. “This is the type of E. coli strain that can cause death, or massive kidney failure.”

News of possible contamination came March 28, when Rich Products announced a voluntary recall of several products manufactured under the Farm Rich and Market Day brands at the Georgia plant where the company has operated since 2002.

Thursday, Rich Products expanded its recall to cover all products made at the plant between July 2011 and last month.

“It’s out of an abundance of caution that we recalled all of our products produced at that plant,” Gram said.

The recalled products include Mini Pizza Slices, Mini Quesadillas, Stuffed Crust Pizza Dippers, Philly Cheese Steaks and Mini Bacon Cheeseburgers.

Of the 10 million pounds produced over 21 months at the Georgia plant, about 7 million pounds was caught before it made its way to cafeterias or store shelves, Gram said. Three million pounds was purchased, and much of that likely has already been consumed, he said.

About 300,000 pounds of the recalled products was distributed to schools across the country, including here.

Cooking food thoroughly will kill E. coli, which has been spread through contaminated fruit, vegetables and meat; through the drinking of lake water, as by swimmers; and through contact at petting zoos, said Dr. Gale R. Burstein, Erie County’s health commissioner.

Burstein said people need to wash produce before eating it, cook meat thoroughly, and wash their hands and any surfaces that come into contact with raw meat.

There are a number of strains of E. coli, and only certain strains produce the toxin that can lead to severe abdominal pain, diarrhea and the destruction of red blood cells that can cause kidney failure, she said.

So far, the 27 cases in 15 states linked to this rare strain of E. coli involve patients ranging in age from 2 to 75.

The patients reported initially getting sick between Dec. 30 and March 18, with nine requiring hospitalization and two suffering hemolytic uremic syndrome, which can lead to kidney damage, the CDC said.

The two confirmed cases of E. coli infection, in Texas and New York, were traced to frozen mini chicken quesadillas and frozen mini pizza slices taken from their homes, according to the CDC.

In an unconfirmed local case, Robert Ormsby Jr., a 19-year-old Niagara County Community College student, said he got sick after eating the quesadillas and pizza slices, which his family bought at the Walmart in North Tonawanda, according to Dietrich, his attorney.

Ormsby started feeling sick around March 15, and he went to the VA hospital March 19 for treatment of a painful upset stomach and diarrhea. A doctor at the VA, where Ormsby is eligible for treatment because his father is a veteran, prescribed antibiotics and discharged him the same day.

About a week later, Ormsby started throwing up, and he was concerned enough to return to the VA hospital March 27, when he was admitted to the intensive care unit.

“He has been in kidney failure. He has required dialysis,” Dietrich said, as well as transfusions of blood and plasma.

Ormsby left the ICU on Saturday, his 19th birthday, but he remains hospitalized in a weakened state.

Shortly after Ormsby was admitted to the hospital, his mother, Tammy, learned about the recall of the Farm Rich products “and put two and two together,” Dietrich said.

They’re not sure which of the two Farm Rich products made Ormsby sick, but Dietrich said an investigator from the state Health Department went to the family’s home to collect samples of the food for testing.

The family has retained Dietrich, who notified Rich Products of his intent to file a lawsuit on Ormsby’s behalf.

Dietrich said a middle-aged man who lives in Springville called him last week to say he became ill after eating Farm Rich mini quesadillas and mozzarella bites that he bought at the Walmart Supercenter in Springville.

“He was bedridden as a result of the infection,” though not hospitalized, the attorney said.

Rich Products has responded to the possible E. coli contamination by stopping production at the Georgia plant March 28 and by conducting a thorough cleaning and investigation of the facility under the guidance of the federal Food and Drug Administration, Gram said.

This investigation found “no evidence” tracing the E. coli contamination to the plant, Gram said. Rich Products now is looking at all possible causes of the outbreak, including companies that supply the raw ingredients, he added.

The company has focused on responding to the contamination and ensuring the safety of its customers, Gram said, and has not yet estimated the cost of the recall.

Area schools bought food later recalled

The following schools and districts are believed to have received the Farm Rich products

• Akron Central Schools

• Amherst Central Schools

• Depew Schools

• Frontier Central Schools

• Queen of Heaven School, West Seneca

• St. John the Baptist School, Town of Tonawanda

• St. Mary of the Lake School, Hamburg

• Sweet Home Central Schools