Los Angeles International Airport evacuated a terminal on Monday after a possible carbon dioxide leak sickened at least four people, including one person in "grave condition," officials said.
Terminal 8, utilized by United Airlines, was cleared of all passengers around 8 a.m. local time as firefighters investigated the apparent leak, the airport said.
Three people were in mild distress and one in "grave condition" due to the leak, the Los Angeles Fire Department said.
Fire officials said no escalating or off-site hazard has been identified.
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While officials have not stated where the gas leaked from, local reports say it appears to have taken place during construction work and affected construction workers.
This is a breaking news story; check back for updates.