Their pain is believed to be due to some apples they'd eaten.
Three students at Ballou High School were treated for nausea and stomach pains Monday after eating apples brought in by a teacher, News4's Jackie Bensen reported.
One student had trouble breathing.
The D.C. Department of Health said it is still investigating and has not identified the apples as the source of the illness. The school's air quality was checked and found to be normal. The DOH Food Safety team inspected the school's kitchen and did not find any positive results associated with the illnesses.
"The story is a teacher, every year during test time, brings in apples from her home orchard back in Pennsylvania, and she gives them out to the students," D.C. Fire and EMS Battalion Chief Maxim Saunders said.
Investigators located the rest of the apples, tested them and determined they were OK.
"We're starting to think now that maybe these particular students were allergic to apples or whatever type of pesticides or whatever may have been used on the apples," Saunders said.
The students were transported to local hospitals. Department of Health epidemiologists are working with the hosptial and the public health laboratory to investigate further.
The teacher who gave the students the apples is said to be very upset by the illnesses, Bensen reported.
Stay with NBCWashington.com and NBC4 for more as the story develops.