Nearly two dozen students fell ill after eating candy bars that were sold as a school fundraiser, and police have opened a criminal investigation, authorities said Thursday.

The 21 Liberty High School students who ate the chocolate-covered caramel bars were treated at a hospital Wednesday for nausea and vomiting, though none appeared to have suffered any lasting effects, police said.

Several people were interviewed, Clarksburg Police Chief John Walker said Thursday. No arrests had been made.

Investigators with the U.S. Food and Drug Administration are helping, but lab tests on the Kathryn Beich brand candy bars will not be available for several days, Walker said.

Carl Friebel, superintendent of Harrison County schools, said nothing suggests a broader problem with the Kathryn Beich brand.

"We think the candy was a vehicle, not the cause," he said.