Helena High School students have returned to class after a brief evacuation Thursday morning. The students were evacuated to a nearby field for a short time after someone called 911 to report the smell of gas in one of the offices. Firefighters searched the building, and the school district's Superintendent Tyler Ream said the school received the "all-clear" at 11:45 a.m. This happened several times last spring at several other Helena schools, which were also evacuated at the time.