DURHAM (WTVD) -- About 1,400 students were evacuated from Southern High School in Durham Wednesday morning due to a natural gas leak.
When fire crews and paramedics arrived at the high school, they thought they were responding to a medical call.
"This one was a little unusual. It came in as a sick call," explained Deputy Fire Chief Christopher Iannuzzi.
The leak was detected around 8:30 a.m.
Before firefighters arrived, several people at the school had complained of headaches, nausea, and dizziness.
"Durham County EMS evaluated and monitored a total of 9 patients, and none of them needed treatment or transport," said Katherine Mellow with Durham County Emergency Medical Services.
Emergency workers quickly discovered an open valve in a science laboratory at Southern High School that caused a slow leak of natural gas. As a precaution, the building was evacuated and the 1,400 students waited for the all-clear at the school's football field.
While using gas meters that can detect combustible gas, it would take nearly two hours for firefighters to safely monitor the air inside the building. They found find low levels of gas and a minimal risk of explosion, according to Deputy Fire Chief Iannuzzi.
Classes resumed after the evacuation. No other injuries were reported.