(CNN) – The four people hurt in an apparent gas leak on Monday at Los Angeles International Airport were all airport employees, according to an update provided by the Los Angeles Fire Department
The condition of the most severely sickened victim has been upgraded from grave to critical following the incident.
A woman and three men were working in or near a utility room “when a popping sound was heard, and the apparent release of Carbon Dioxide vapor took place,” the LAFD report said.
The most seriously injured man, described as being in his 50s, was found not breathing and without a pulse inside the utility room. CPR was immediately performed and advanced life support given by emergency responders as he was taken to a nearby hospital, the fire department shared.
“LAFD Hazardous Materials experts have closely examined the area with sophisticated instruments, and discovered only trace residue of Carbon Dioxide remaining within the utility room,” said the LAFD.
Portable fans are being used to further ventilate the immediate area.
All other terminals and flights are operating normally, according to a tweet from LAX airport.
The terminal was cleared of passengers due to a hazardous materials investigation, the airport tweeted earlier on Monday.
The Federal Aviation Administration issued a ground stop for United Airlines as a result of the emergency. Terminal 8 primarily services United flights.
Flights that were already in the air headed to the airport will land as planned, the airport tweeted. Others will depart after 10 a.m.
“Check your flight status with the airline directly for the best information,” the tweet said.
Passengers passing through security bound for Terminal 8 were being held in Terminal 7 after screening, Transportation Security Administration spokesperson Lorie Dankers said.
Dankers said all TSA employees are OK, and the incident did not involve a TSA checkpoint.