A geology professor demonstrating an instrument for measuring radioactivity to a high school class accidentally found a long-abandoned canister containing radium, officials said.

The canister posed little danger, and no injuries were reported, said Al Warlick, director of public affairs for the state Division of Crime Control and Public Safety.

The canister was discovered Tuesday when geologist John Callahan, who had shown a science class how a Geiger counter reacted to uranium rocks and put the instrument against the classroom wall to show normal readings. Instead of remaining silent, the device went off.

Behind the wall was a storeroom where officials found a canister marked "Army Corps of Engineers" and dated 1944.

The canister had apparently been on a shelf since the school opened in 1965, Watauga High School principal Jim Day said.