City and other officials are investigating why a crane's steel load hit and shattered windows on the 45th and 46th floors of 4 World Trade Center on June 27th. There were no injuries, said a spokesman at the FDNY, which received the call about the incident at 11:30 a.m. Tishman Construction, the CM on the 72-story tower, says it has suspended steel lifts pending the investigation, is inspecting the entire facade of the building and reviewing protocols for evaluating weather conditions.

Photo by Joe Woolhead

The tower recently held a topping out ceremony to mark completion of steel erection.

"A sudden gust of wind caused a steel load to impact a curtain wall panel on the south side of tower 4," a Tishman spokesman said in a statement. This resulted in glass falling onto Liberty St., which was closed at the time and is protected by a construction shed, he said.

The National 9/11 Memorial & Museum, which shares the 16-acre WTC site with 4 WTC, issued a closure notice for the rest of the day due to the incident.

The accident occurred one day after a worker at the tower was hospitalized after slipping and being injured by a small steel rod that he was carrying in his pouch at the time, said Tishman Construction in a statement on June 28th.

Earlier this year, the cable of a crane snapped as it was carrying steel beams up 4 WTC, causing the beams to fall about 40 stories. No one was reported injured in that incident and officials said in March that it would take months to determine the cause.

Meanwhile, 4 WTC, the smallest of the four planned on the WTC site and the first set for completion in the fall of 2013, held a topping out ceremony on June 25 to mark completion of steel erection.