Firefighters evacuated about 250 people from the Cottonwood High School gymnasium Monday night after an apparent natural gas leak forced a Christmas concert to end early.

It was the second time in four days firefighters and Mountain Fuel emergency workers cleared the high school gym so they could check for gas leaks.Classes resumed Tuesday as scheduled, school officials said.

Friday night, the joints of natural gas pipes feeding one of the school's boilers leaked, allowing the gas to backdraft into the gym. The emergency forced the end of a basketball game between Cottonwood and Layton high schools during the game's first quarter.

Mountain Fuel workers taped the pipes and ventilated the boiler room over the weekend. But at about 8:30 p.m. Monday, the smell of gas again permeated the gym, said Capt. Rex Sylvester of the Salt Lake County Fire Department.

Sylvester said officials weren't positive the smell actually came from a gas leak. The gym was cleared as a safety precaution, he said.