BERKELEY -- Police and clean-up crews staged a surprise raid early Friday, removing a makeshift encampment that had sprung up below a UC Berkeley campus grove where demonstrators have taken up residence to protest a plan to cut down the trees.

UC Berkeley police spokesman Mitch Celaya said the encampment had become a public safety concern with students scheduled to return Tuesday for classes. Celaya said university workers filled two flatbed trucks with tents and tarps, tables and chairs, stoves and barbecues.

"It was like a circus tent," Celaya said. "They had tarps they had made in a tent fashion, over about a 20- by 40-foot area. It was becoming a place of lodging."

He said the objective this morning was to remove things, not people.

Celaya estimated that three or four protesters at any given time are staying in the trees, which are slated for removal under the university's construction plans for the Memorial Stadium area.

"We're not going to go up and get them," Celaya said. "They're fairly high up. It's a personal safety risk not only to them but to us."

The protest began in early December and as of Friday four people were living in three different trees in a grove of live oak trees on the east side of the campus.

The trees are to the west of the university's Memorial Stadium, Celaya said.

The university plans to build a new sports training facility and a new four-story underground parking lot with more than 900 spaces and retrofit Memorial Stadium.

The plan also calls for a new building that would combine functions of UC Berkeley's law and business schools.

In addition, the plan calls for cutting down 38 live oak trees on a hillside just west of the stadium.