MULTNOMAH FALLS, Ore. -- A large rock fell onto the popular Benson Bridge over Multnomah Falls Thursday but no one was injured.

The iconic bridge over the picturesque Multnomah Falls has been closed indefinitely, along with the viewing plaza, due to the damage.

The hole is about three feet wide. No one knows exactly when it happened, but it was likely some time overnight or early Thursday morning.

The U.S. Forest Service has inspected the damage. It said the rock face at the falls is constantly being worn away from the force of the water, but seldom is the damage this severe.

It really looked like something fell over the cliff side and it broke off, one onlooker said.

A portion of the cement railing was also knocked out. The Forest Service has closed the bridge, along with the Wahkeena/Multnomah Falls loop trail and Larch Mt Trail #441 from Multnomah Falls plaza to the Gorge 400 trail.

Engineers will further evaluate the damage Friday and decide what repairs must be made before the area can safely be re-opened.

More: USFS closure alert

Multnomah Falls is the most visited natural attraction in Oregon with more than 2.5 million visitors a year. It is the second highest year-round waterfall in the United States and the highest waterfall in the Columbia River Gorge with a total drop of 620 feet.

The Benson Bridge is a popular tourist attraction and photo spot. It was built in 1914 by Italian stone masons just above the Multnomah Falls Lodge.

This isn't the first time a large rock has fallen on the Benson Bridge, but it has been quite a while.

In 1995, a boulder the size of a school bus slid from the face of upper Multnomah Falls and dropped into the upper plunge pool. This created a splash of 70 feet and sent rocks flying over the bridge.

A large wedding party just happened to be on the bridge for photos when the boulder fell and 20 people were injured by rock shrapnel, including the groom. No one had serious injuries though, and the bride and groom's story was featured the next day in the newspaper.

This winter has had some tough moments for tourists at Multnomah Falls and the gorge.

In December, the viewpoint, and path leading up to it, became encased in ice. This made for a slippery trek for determined tourists who still ventured up the hill to get photos.

Video:Tourists slip on ice at MultnomahFalls

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