Health officials say at least 50 people were treated after a reported salmonella infection at a weekend picnic in central Pennsylvania.

The Centre Daily Times reports that Grace Prep High School said in a Facebook video Saturday that at least half of the 100 to 150 guests at a going-away picnic for a longtime teacher Friday had fallen ill with symptoms of nausea and vomiting.

Mount Nittany Medical Center said its doctors had seen 50 patients associated with a common activity since Saturday who had gastrointestinal-type symptoms.

School founder Bob Gresh said the bug had been confirmed to be salmonella. The source is unknown, but state health officials are testing samples of food from the picnic.