Seven students and two staff members were taken to a hospital Thursday after the smell of gas led to the evacuation of Colonel Zadok A. Magruder High School in Rockville, Montgomery County fire officials said.

The evacuation, minutes before afternoon dismissal, was ordered after the odor of gas was detected on the second floor of the school.

Officials believe the odor was from a sewer pipe in a classroom. That pipe was capped and school staff are handling the issue.

Those who received medical care were evaluated for injuries that were not life-threatening, fire officials said. The school was cleared for reentrance shortly after 3:30 p.m., according to school officials. One after-school activity was canceled.