(AP) -- Two window washers were trapped on a dangling scaffold nearly 70 stories up the new 1 World Trade Center tower for nearly two hours on Wednesday before firefighters sawed through a thick double-layered window to reach them.

The dramatic rescue, coming a little more than a week after the nation's tallest building officially opened, was followed by throngs of New Yorkers on the ground and many more around the world watching on live TV.

The window washers, Juan Lizama and Juan Lopez, were working on the lower Manhattan building's south side when one of the platform's four cables abruptly developed slack, Fire Commissioner Daniel Nigro said. The open-topped platform tilted sharply and swayed slightly between the 68th and 69th floors, he said.

"It suddenly went from horizontal to nearly vertical," he said.

A fire department photo shot from inside the building shows the scaffold platform hanging precipitously, with the Statue of Liberty appearing tiny in the distance.

About 100 firefighters rushed to the skyscraper, some of them lowering ropes from the roof so the workers could secure themselves and a two-way radio for them to communicate, Nigro said. The workers, who have more than 20 years of experience between them, also were harnessed to the platform, and the building's owner said they had all the requisite safety gear and training.

Firefighters used diamond cutters to saw through part of a two-layered, inch-thick glass window on the 68th floor, which is still under construction. They shattered the glass in place, then carefully pulled the broken pieces into the building.

Firefighters also began inching another scaffold down the building as a backup rescue plan, but they were able to bring the workers to safety through the roughly 4-by-8-foot window hole.

"It was a fairly straightforward operation," said Battalion Chief Joseph Jardin, who oversees the fire department's special operations.

Officials stressed that firefighters had trained for various emergencies at the tower, the centerpiece of the rebuilt World Trade Center.

Firefighters generally seek to cut out windows to make such rescues, but Nigro noted the trade center's thick glass: a double-paned inner layer and an outer pane.

"And, of course, they were 68 stories up," he said. "That presented a little bit more of a challenge."

Lizama and Lopez were checked out at a hospital and were released. Their union, Service Employees International Union Local 32BJ, said it makes sure workers follow rigorous safety protocols.

The building's owner, the Port Authority of New York and New Jersey, said it was suspending window cleaning there while investigating what happened. The window washing company and the rig's supplier, which built and repaired scaffolds involved in two other high-profile accidents in recent years, didn't immediately return calls seeking comment.

Officials haven't determined what caused the cable problem Wednesday. The cables are controlled from the scaffold vehicle, the fire commissioner said.

It was unclear whether anything about the design of the 1,776-foot, 104-story skyscraper complicates working the window washing scaffolds, which went into service in June.

The window washers were working for Upgrade Services Window Cleaning, which services other prominent New York skyscrapers, including 4 World Trade Center.

The scaffold supplier, the Tractel Group, was fined $21,000 in 2008 after a scaffold it had repaired the year before gave way with two window washers aboard while they worked on the 47th floor of an upper Manhattan building; one worker died. Tractel also built a scaffold that snapped 500 feet above the ground last June in midtown Manhattan, leaving two workers dangling; they were rescued after firefighters cut through glass.

During Wednesday's rescue, people on the ground were moved back in case glass began flying. Office workers and construction workers streamed onto a nearby street, their necks craning to watch the scaffold as it waved in the wind.

Window washer Ramon Castro, who stood with the onlookers before the rescue, said he hoped the workers were able to stay calm.

"When you start panicking, it makes things worse," he said, adding that he had encountered dangerous situations on the 22nd and 25th floors of other buildings. "You have to say your prayers."

The silvery $3.9 billion skyscraper, which rose from the ashes of the Sept. 11, 2001, terror attack, opened last week to 175 employees of magazine publisher Conde Nast. Steps away are two memorial fountains built on the footprints of the decimated twin towers, a reminder of the more than 2,700 people who died in the attack.

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Associated Press writers Kiley Armstrong, Verena Dobnik, Deepti Hajela and Jennifer Peltz contributed to this report.