Occupy DC protesters sit atop a wooden structure at their encampment in Washington's McPherson Square on Sunday.

Washington (CNN) -- An hours-long standoff between police and Occupy DC protesters ended Sunday night after officers forcibly removed several people clinging to a wood structure erected earlier in the district's McPherson Square.

A total of 31 people were arrested over the course of the day, according to U.S. Park Police spokesman Sgt. David Schlosser.

The standoff started shortly before 11 a.m. as park police surrounded the structure built overnight as a place where protesters could stay warm in the winter and hold their daily general assembly meetings, according to Wade Simmons, one of the Occupy demonstrators.

Police ordered the structure taken down around noon Sunday, a post on the Occupy DC website reported, but some people remained perched on top of or inside the building, which was donated by a father-son architect team. As many as 200 people gathered at the park to watch the standoff.

Schlosser said the protesters had not gone through proper permitting procedures for the structure and "police had safety concerns regarding structural integrity."

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