State health officials say they are consulting with the U.S. Centers for Disease Control and Prevention about whether further testing is warranted to determine whether a beet salad caused 22 elementary school students to get sick last week.

Tests conducted by the Maine Center for Disease Control last week were inconclusive, which means the beet salad served at the Reiche Elementary School in Portland was neither exonerated nor proven to be the cause of the outbreak. State officials said the investigation is ongoing, but would not provide details or make investigators available for interviews.

“At this point, it is not clear that this is a food-borne illness or a case of food poisoning,” spokesman John Martins said in an email. “We do not know the cause.”

Sixteen students at the school began vomiting an hour after eating lunch on March 10, and six more complained of stomach pain. The illness lasted only a few hours, no students required treatment and all but one returned to school the next day, according to the school district.

Some parents are disappointed by the lack of a clear cause, but they strongly suspect the beet salad served in the school cafeteria that day. They aren’t too concerned, however, because it appears to be an isolated incident, according to the president of the Reiche Parent Teacher Organization.

“It would be nice to know,” said Leah Whalen, whose daughter got sick after eating the beet salad. “I think parents would be more worried if this was part of a pattern. It hasn’t had any longterm effect on my kid, besides a possible beet aversion.”

Such sudden outbreaks appear to be rare in Maine schools.

There has been one confirmed case of a foodborne illness outbreak in a Maine school since 1998, according to the U.S. CDC. The online database doesn’t name the schools or the locations, but in April 2001, 70 people contracted Norovirus from lettuce served in a Maine school.

The U.S. CDC database lists four possible but unconfirmed foodborne illness outbreaks in unidentified Maine schools, including 54 people getting sick after eating chicken fajitas in June 2001.

State officials are providing little information about their investigation into the Reiche school episode. All inquiries were referred to Martins, who required questions be sent in writing.

“As this investigation remains open, we cannot provide anything more than the information we have already provided,” Martins said in an email Friday. It wasn’t clear how releasing details about the state’s response would compromise the investigation.

MANY DETAILS STILL UNKNOWN

Martins would not directly answer such questions as how many children were interviewed, whether the sick kids were all tested for bacteria, and what other theories officials have to explain 22 students getting sick at the same time.

“Without testing an individual who is currently ill, it is hard to determine what to look for when testing food,” Martins said in an email Thursday. “The tests conducted here in Maine (on the beet salad) ruled out the majority of foodborne bacteria that could be linked to an illness. Any further testing to rule out bacteria would require more complex testing done by the U.S. CDC.”

A message left with the U.S. CDC seeking additional information was not returned.

Whalen said many parents are convinced the beet salad caused the illness, even though some kids who ate it didn’t get sick.

Whalen said her daughter always brings her lunch to school, but sampled the beet salad, which was made in the Portland school district’s central kitchen and flavored with apple cider vinegar. The beet salad was the only food her daughter had that was also consumed by the other kids who got sick, she said.

Students in more than one classroom all felt ill and went to the nurse’s office about the same time, which seems to reduce the chance that the sickness was a case of sympathy vomiting – a phenomenon made famous in the movie “Stand by Me.”

State and local health officials inspected the Reiche school kitchen, as well as the central kitchen on Waldron Way, where all public-school meals are prepared. The central kitchen passed its inspection, but the Reiche school failed with four critical violations. School officials have said those violations have been corrected.

School Superintendent Emmanuel Caulk denied a request to interview a Reiche school employee and the head of the school food services division. “There’s nothing for us to add or comment on at this time. Once we have more information, we will share,” he said in an email.

William Marler, a Washington-based attorney who specializes in foodborne illness outbreaks, said disclosing information in such cases better serves the public, especially because this was a limited event confined to a specific population.

“That seems counterproductive to me,” Marler said.

Based on what has been reported, Marler believed there was 99 percent chance it was some sort of staph infection from a worker with a cut who didn’t wear gloves, or from a chemical contamination of the food.

“It appears, from what you described, that it was probably a food handling error,” he said.

Even though the students recovered quickly and no others have fallen ill, Marler said, it’s important to determine what happened so future outbreaks can be prevented.

“The next time it could be salmonella, listeria or E.coli,” he said. “Then you will have kids in the hospital. Then you’ve got a real mess.”