The eighth-graders from West Valley Middle School in Knoxville, Tenn., were all wearing blue school T-shirts during a trip to a Civil War re-enactment Friday when they complained of nausea, dizziness and a heavy feeling in their arms and legs, The Knoxville (Tenn.) News-Sentinel reported Wednesday.

The cause of the illnesses has baffled health officials so far, said Ranee Randby, a Knox County, Tenn., Health Department spokeswoman.

"We've tried to be as open-minded as possible, and we've tried to not preclude anything," she told the newspaper, with one possibility being that the students got queasy after hearing about graphic Civil War-era surgeries. But, she added, some of the children didn't become sick until after leaving the site.

Tests on the T-shirts were being performed this week, the News-Sentinel reported.