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Gas Scare Empties School near Calif. Blast Site

School children evacuate an elementary school in San Bruno, Calif., Thursday, Sept. 16, 2010. Portola Elementary School, close to a gas line that exploded last Thursday, has been evacuated after a student's mother reported smelling an odor. Authorities say they did not detect natural gas in the area but evacuated the school as a precaution. (AP Photo/Paul Sakuma)
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Updated at 3:14 p.m. ET

An elementary school near the site of last week's deadly gas line explosion and fire in a San Francisco suburb was evacuated Thursday morning after a strong odor permeated the school. The odor turned out to be not natural gas but carbon dioxide, which officials described as harmless.

(Scroll down to watch video from CBS News Station KPIX-TV in San Francisco)

Still, the evacuation reflects the community's increased sensitivity after a gas line ruptured, shooting a massive fireball into a residential neighborhood. The blast and resulting fire killed at least four people and burned nearly 40 homes.

Students and staff at Portola Elementary School in San Bruno, Calif., were evacuated to another school, CBS News Station KPIX-TV in San Francisco reports.

Cheryl Peruchetti, an official for the San Bruno Park School District, told KPIX-TV that classes were canceled for the day at the elementary school, which is located less than a mile from the Sept. 9 blast site.

A spokesman for Pacific Gas and Electric, the utility company being investigated in last week's blast, said the odor was carbon dioxide from the school's heating system and was not dangerous. Spokesman Kory Raftery said crews didn't detect a leak after checking the school's meters and gas lines.

Additional crews were brought in to verify that there wasn't a gas leak, gas company spokesman Jeff Smith told KPIX-TV. The company encouraged "all folks to stay a safe distance from the area" while the investigation continued, KPIX-TV reports.

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