Sol LeWitt’s “Wall Drawing No. 681 C,” a wall divided vertically into four equal squares separated and bordered by black bands, collapsed Friday. (National Gallery of Art)

Just before noon on Friday, as a group of students toured the National Gallery of Art’s East Building, the wall behind them began to collapse.

Or at least, that’s what it looked like at the time.

Bystanders heard the snap. They saw the tiny fractures. And Sol LeWitt’s “Wall Drawing No. 681 C,” all 10 feet by 37 feet of it, began to fall slowly toward the teenage boy and girl standing in front of it.

To save the falling work, they lunged forward to push it up.

“Don’t touch the painting!” a guard yelled out of habit, until he, too, noticed the installation in flight. He moved swiftly, just as the students did, toward the LeWitt, and then there were six palms touching the work, committing the cardinal sin of gallery-going.

Two more boys joined the group, then several others arrived. Help eventually came minutes later from workers with wedges and screens that are now holding the installation up for the remaining hours of its public display.

A photographer happened to capture the event, which showed seven people of various ages holding up the massive work. He declined to offer the photos for publication. The installation will be removed Saturday morning before the gallery opens, a dramatic end for a LeWitt piece now heading into storage.

This painting, hanging in the same spot for 20 years, was never meant to be there permanently. “It was only meant to be temporary,” said Deborah Ziska, spokeswoman at the gallery. And, to add to the gallery’s luck, the plywood installation, separated into four equal squares of neon-colored stripes, wasn’t even made by LeWitt. Or it was, but he didn’t touch the wall-size ink work with his own hands. Illustrating his belief in artist as thinker, not craftsman, LeWitt, the minimalist artist who gained notoriety in the 1960s, made instructions for how a group of people might make this artwork.

“The artwork is represented in the gallery’s collection by a certificate and a diagram,” Ziska said. “A team of artists from LeWitt’s studio executed this drawing in August of 1993.”

Still, falling art is code red for any gallery, a rare emergency that curators hope never happens. The National Gallery has never had a painting or sculpture fall before, even during Washington’s well-remembered earthquake of 2011. The gallery is raising the roof of one its galleries for the upcoming “Diaghilev and the Ballets Russes” exhibition in May, but there is still no consensus on why the painting fell.

“It could be a confluence of different factors,” Ziska said.

The gallery does not comment on the value of the work, but one onlooker said that the damage seemed minimal. Ziska also said that the work did not come fully detached and probably would not have fallen to the floor. As for whether the children acted appropriately, touching the massive work with their fingers, Ziska praised their quick thinking:

“We applaud the children for doing what they thought was a good thing to do.”