(CNN) -- More than 150 students at the University of California at Berkeley took over a campus building Thursday to protest a proposed 81% increase in tuition fees, university officials said.
UC-Berkeley spokeswoman Callie Maidhof described the scene as "an open occupation with people coming and going" at Tolman Hall on the campus that has been known for decades as a hotbed of student activism and protests.
The tuition increase proposed by the board of regents would be phased in over a four-year period.
Maidhof added that when the protest began Thursday afternoon, campus police initially resisted the demonstrators and used pepper spray at one point. The university maintained a hands-off approach after that, but according to Maidhof the situation could change at the building's scheduled closing time of 9 p.m. (midnight ET).
As evening fell, there were between 60 and 70 students occupying one of the classrooms and another group was participating in a teach-in outside on the lawn.
Helicopter aerials of the scene from CNN affiliate KTVU showed a few protest banners hung from windows of the classroom building.