The Ledge on the 103rd floor of the Willis Tower in Chicago was closed Thursday morning, one day after the protective coating over the thick glass shattered beneath the feet of a California family.
Brian Rehme, a spokesman for public relations firm FleishmanHillard, representing the tower, says The Ledge boxes remain structurally sound.
Alejandro Garibay told NBC Chicago that he, his brother and two cousins were on The Ledge that juts out of the building around 10 p.m. Wednesday when they heard cracking.
"Crazy feeling and experience," Garibay wrote in an email to the TV station. "I walked them over so they could see and they were totally shocked and asked us to step away and then proceeded to start calling staff and techs and I don't know who else. When we pulled our phones to start recording and take pictures they asked us to leave right away."
The Ledge opened in 2009.