Inspectors work inside the Washington Monument in Washington, DC
Inspectors work inside the Washington Monument in Washington, DC, in this handout taken and released on August 24, 2011. The earthquake that shook much of the East Coast cracked one of the stones at the top of the monument, a National Park Service spokesman said. REUTERS/National Park Service

The Washington Monument, the iconic symbol of the nation's capital, will remain closed indefinitely because of damage sustained in the 5.8-magnitude Virginia earthquake in August.

The US National Park Service said in an announcement on Monday that a debris field, made up mostly of mortar that had fallen during the quake, was found at the base. More debris was found inside the monument.

The Park Service released a dramatic video on Monday taken from the security camera at the observation deck near the top of the structure during the earthquake (view the video below). The video shows debris falling from the ceiling, the structure shaking violently, and horrified and confused visitors racing down the stairs, running for safety.

There were about two dozen people on the observation deck on Aug. 23 when the quake struck outside of Mineral, Virginia, roughly 90 miles south of the nation's capital.

National Park Service ranger Niki Williams can be seen looking up after the shaking continues, but there is no panic. She calmly ushers the tourists down the stairs, just as they are pelted by falling debris.

Two tourists are seen falling down briefly before returning to their feet and joining the others on the crowded stairs.

Williams told the Early Show that she was initially quite scared, but snapped back into action.

I realized I had to take care of these 20 people. I was responsible for them, Williams said. So I go down to that next level, you see me going down the stairwell to open up the emergency exit and get them down the stairwell.

I thought we were under some sort of attack, she added.

I did not have any indication of what had happened until about two minutes after, Williams said. I was walking down the stairwell to assist a visitor and a park police officer came across my radio and notified me that it was an earthquake that had happened, which calmed me a little bit. But then I realized there could be aftershocks while I was in the stairwell.

No one was injured during the earthquake, but some elderly visitors were forced to walk the 897 steps to the ground level.

The National Park Service has worked with an engineering firm since the late-August earthquake. Together, they have assessed the extent of the damage and what it will cost to fix it.

The monument's elevator system broke in the quake and is only operating to the 250-foot level, The Washington Post reports. The system is believed to have been damaged by its counterweights as the structure shook.

Four cracks were discovered in the marble monument just after the quake, but engineers assured the National Park Service that the monument was structurally sound. They erected a 100-foot-radius fence to prevent any falling debris from injuring visitors.

Brandon Latham, a mountaineering and rope-rigging ranger from Denali National park in Alaska was brought in this week to assist the engineers in rappelling down the sides of the monument to conduct a closer inspection. A team of four will spend the next five days assessing the damages.

The Washington Monument was built between 1848 and 1884. It stands just over 555 feet tall with walls that are 15 feet thick at the base and 18 inches at the top.

Built to commemorate the first U.S. president, General George Washington, the obelisk stands tall on the west end of the National Mall. It is the tallest building in Washington (the Heights of Buildings Act of 1910 prevents any new buildings from surpassing the monument in size or obstructing it from view) and the world's tallest stone structure.

Have a look at the surveillance footage from the top of the Washington Monument during the Virginia earthquake: