DULLES, Va. - Rescuers trying to find a worker trapped in a collapsed tunnel he had been digging at Dulles International Airport worried Thursday as the ground grew more unstable.
Crews at the construction site did not know if the man was still alive.
''We're treating this as a rescue operation,'' said Tara Hamilton, spokeswoman for the Metropolitan Washington Airports Authority.
Workers were attempting to install supports and then planned to excavate by hand to avoid vibrations that would further weaken the tunnel.
The tunnel, about 15 feet underground, collapsed at about 7 p.m. Wednesday.
Three other workers escaped without injury, according to the tunnel contractor, Kiewit Construction.
The tunnel, part of a $3.4 billion airport expansion, is to become a walkway for passengers between the main terminal and Concourse B.
The rescue units included the Fairfax Urban Search and Rescue Team, an elite group often called in to assist in rescue efforts after earthquakes and bombings worldwide, according to Terry Williams, night supervisor of Fairfax County Public Safety.
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On the Net:
Dulles International Airport: http://www.metwashairports.com/Dulles