The NTSB and OSHA are involved in the investigation. We still don't know what exactly caused the accident that killed one worker and injured another.
The accident happened almost 40 feet in the air.
"Up on that monorail, it's pretty high up there," airport employee Jim Johnson said. "It's gotta be real dangerous work."
Travis Turner, 57, was killed, and a second worker has serious head injuries. Houston firefighters had to use aerial ladders, ropes and a stokes basket to get to the victim.
"When you have a patient that's 30 feet up in the air and can't move, it takes some equipment to set that up and get them handled safely," Houston Fire Department Deputy Chief Terry Stone said.
Airport spokeswoman Marlene McClinton says the two contract workers were doing routine work on the elevated portion of the automated people mover (APM) track outside Terminal B when they were struck around 11:30am Tuesday.
"I don't know specifically what the job was that they were doing but they have an assortment of duties and things that they work on on those trains," McClinton said.
McClinton says employees were working on a city project managed by Continental. The victims worked for subcontractors.
The injured worker is employed by Weber Construction, where a spokesperson says he is a foreman on a runway project. The spokesperson says they, too, are trying to piece together how their employee was injured.
The tram system can travel up to 33 miles per hour; while it can be run manually, airport officials say, in this case, it was on automation. The system can carry a capacity of 5,000 passengers per hour each direction.
The system has been temporarily suspended and buses are being used to transport travelers.
A hotel worker who witnessed the rescue told Eyewitness News it's not uncommon for people to walk on the elevated tracks.
The airline issued a statement that read, "Continental is working with the authorities in their review of the accident and we extend our deepest sympathy to the family members of those involved."
McClinton said the trains were down for the rest of the day as the investigation continued. The airport has been moving passengers by bus.