Tests came back inconclusive on a pickled beet salad served at a Portland, Maine, school where more than 20 students became sick, the Maine Center for Disease Control and Prevention says.
The Portland Press-Herald reports the tests were part of an investigation into whether the salad sickened 22 students at Reiche Elementary School on March 10. The salad was not served at any other school in the city on that day.
Officials say students became sick about an hour after eating lunch. Sixteen of them vomited while the others complained of stomach pain. All but one returned to school the next day.
Maine Center for Disease Control and Prevention spokesman John A. Martins says there has been "no determination of the onset of the illness" that affected the students.