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 ill victim has been upgraded from grave to critical after 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.
The incident occurred in Terminal 8 near the baggage area. The terminal was cleared of passengers after the incident. The area reopened around 1 pm ET (10 am PT), according to a tweet from LAX airport.
A Federal Aviation Administration ground stop for arriving United Airlines was also lifted, the airport said.
All other terminals and flights were operating normally, according to a tweet from LAX airport.
“Check your flight status with the airline directly for the best information,” the airport tweeted earlier on Monday.
United told CNN it was “temporarily consolidating” its operations to Terminal 7 and was contacting impacted customers with new departure time and gate information.
Passengers passing through security bound for Terminal 8 were being held in Terminal 7 after screening, Transportation Security Administration spokesperson Lorie Dankers said earlier on Monday.
Dankers said all TSA employees are OK, and the incident did not involve a TSA checkpoint.
CNN’s Marnie Hunter contributed to this report.