ALBANY, Ore. (AP) — Officials say at least 19 students in Greater Albany Public Schools attended a gathering without masks, spurring new COVID-19 cases and setting back progress made toward holding in-person classes.

The Albany Democrat-Herald reports at least three positive cases have been traced to a gathering with students from West Albany High School, South Albany High School and Lebanon High School.

Schools Superintendent Melissa Goff says in addition to the large gathering, another six students should be quarantining.

The students’ families have been contacted by health authorities but according to Goff, some may not be cooperating with efforts to trace the potential outbreak.