LAS VEGAS -- A McCarran Airport official said it was too soon to know what caused Tuesday morning’s collapse of a massive rebar cage at the construction site for its new international terminal.

Five workers were trapped inside the cage. Fellow workers used a crane to lift part of the rebar and cut a hole through another section to free them.

The cage, a cylindrical mesh column of steel rods, is part of a roadway support structure for the terminal. Airport spokesperson Randy Walker said upward of 1,400 similar cages had been constructed at the site.

“Obviously we need to find out what was different about this one,” Walker said at a 10:30 a.m. news conference.

The injured workers were hospitalized, and officials said two suffered critical injuries. None of them have been identified, although Walker said they worked for the Pacific Coast Steel company.

Walker said work will continue at other areas of the site. The $2.4 billion terminal, also known as Terminal Three, is expected to be open to the public in 2012.

This is not the first accident at the construction site. In February, another worker, 25-year-old Byron Souza, was killed at the site. Souza was an employee of Las Vegas Paving.