A little over a year ago, 6-year-old Owen Carrignan of Millbury developed a bad stomachache after returning home from a sleepover. The healthy first-grader was soon hospitalized with severe diarrhea and failing kidneys. He died less than a week later from a foodborne bacteria.

The Boston Globe reports that state health officials recently closed the investigation, unable to identify the culprit food that caused Owen and another Worcester county resident — an unidentified woman in her 30s — to become seriously ill with the same strain of E. coli bacteria around the same time last year.

“We want answers, but there are no answers,” said Michelle Carrignan, Owen’s mother. “I have a hard time food shopping because I keep thinking there could be something here that killed my son.”

“We know that we won’t get to a zero-risk food supply,” said Michael Taylor, the FDA’s deputy commissioner for Foods and Veterinary Medicine. “But consumers have a right to expect that everything that can be done to prevent problems really will be done.”

The new procedures can’t come soon enough for Paul Schwarz, of Independence, Mo., who lost his 92-year-old father in 2011 to a listeria infection traced to a contaminated cantaloupe from Jensen Farms in Colorado.’

The new rules won’t address all food-safety concerns. The produce rules for overhauling the growing practices of farms to prevent contamination, for example, don’t apply to small establishments with less than $250,000 to$1 million in annual sales — the exact amount has yet to be determined.

The rules also exempt produce that is normally not consumed raw such as corn and potatoes, because the likelihood of microbes surviving the cooking or canning process is low.