San Francisco shut down its $2.2 billion transit terminal weeks after opening when a crack was discovered in a support beam

Just weeks after it opened, the $2.2 billion San Francisco's Transbay Transit Center was abruptly closed on Tuesday. A fissure was discovered in one of the building's steel beams.

According to a statement from the Transbay Joint Powers Authority, the beam was located in the ceiling of the third-level Bus Deck, and the closure is "out of an abundance of caution" as inspectors and engineers inspect other beams at the center and work to repair the problem.

The San Francisco Chronicle reported that the beam is among many that support the rooftop garden. Sitting on top of the transit center is a 5.4-acre park space that includes foliage, and numerous seating areas.

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Firemen were on the scene and an officer of the San Francisco Police Department told Business Insider that the building was being evacuated. Police were not allowing anyone near the four-block-long structure.

For a brief time, even one of the streets that leads under the building was blocked. Transit agencies, including Muni and WestCAT were redirecting routes to the temporary Transbay Terminal some blocks away.

The Terminal Center, described as the "Grand Central Station of the West," was a building project nearly two decades in the making. The Center was designed to be a central nexus for local transportation.

Eleven bus lines stop at the station, and transit officials plan to eventually connect it to rail lines.

The Bus Deck is above the ground level. The structure's two other levels are below-ground floors that were designed for rail lines but aren't yet in use.