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CHICAGO (PIX11) – Some California tourists visiting the glass observation deck on the 103rd floor of the Willis Tower in Chicago got the scare of a lifetime.

While taking photos they heard the glass bottom of The Ledge — which juts out from the building 1,353 feet above the ground — begin cracking.

A group of tourists from California took this picture just before they heard they heard cracking. (Alejandro Garibay)

Alejandro Garibay and his group jumped out of the glass enclosure and alerted employees.

According to building officials, however, they were never in any real danger.

A building spokesman said that the glass itself did not break, just the protective covering. (Alejandro Garibay)

“The Ledge was designed with a protective coating that completely covers all glass surfaces to protect against scratches,” Brian Rehme said in a statement, according to WGN. “This coating does not affect the structural integrity of The Ledge in any way. Occasionally, the coating will crack, as it is designed to in order to protect the surface of the glass.”

CHICAGO – JULY 01: Children check out the view from the Ledge, a new glass cube that juts out from the 103rd floor Skydeck of the Sears Tower, during a media preview July 1, 2009 in Chicago, Illinois. The 1,353 foot high observatory will open to the public tomorrow. (Photo by Scott Olson/Getty Images)

The glass of the terrifying tourist draw, which opened in 2009, is 1.5 inches thick and extends 4.3 feet from the building.

On Thursday, the observation deck did remain open, but the viewing area with cracked glass was closed for maintenance.