WASHINGTON – Dozens of U.S. Park Police officers in riot gear and on horseback converged before dawn Saturday on one of the nation’s last remaining Occupy sites, with police clearing away tents they said were banned under park rules.

At least seven people were arrested in the move, which left large swaths of open space at the encampment and raised questions about exactly what would remain.

Police said they were not evicting the protesters. Those whose tents met regulations were allowed to stay, and protesters can stay 24 hours a day as long as they don’t camp there with bedding. Police threatened to seize tents that broke the rules and arrest the owners.

The police used barricades to cordon off sections of McPherson Square, a park under federal jurisdiction near the White House, and checked tents for mattresses and sleeping bags and sifted through piles of garbage and other belongings. Some wore yellow biohazard suits to guard against diseases identified at the site in recent weeks. Officials also have raised concerns about a rat infestation.

By Saturday afternoon, seven were arrested, including four who refused to move from beneath a statute and three who crossed a police line.

One police officer was taken to the hospital, police said, after being hit in the face with a brick.

The National Park Service, which has allowed the protesters to remain in the park for months, has said it will give protesters notice if police decide to clear the park.

Protesters had braced for a confrontation when the park service said it would start enforcing the ban Monday, though no crackdown happened until Saturday.

Despite what police said, some protesters said the crackdown amounted to eviction.

“This is a slow, media-friendly eviction,” protester Melissa Byrne said. “We’re on federal property, so they have to make it look good.”