Portland State University remained at a standstill Tuesday amid the second straight day of a standoff between pro-Palestinian protesters who have occupied the main library and the university’s administrators who have asked police to intervene.

Both Portland Police Chief Bob Day and university President Ann Cudd have said that a police response at the now graffiti-covered library is all but inevitable if demonstrators do not choose to vacate the premises.

The university canceled classes Tuesday and it was not immediately clear when they would resume.

In a letter to the campus community Tuesday afternoon, Cudd asked faculty, students and staff to remain away from campus until “further notice” and said security card access had been curtailed or disabled to university buildings.

“We cannot allow the continued occupation of the library,” Cudd said in an appeal to the protesters posted on Portland State’s Instagram account. In that post, Cudd offered to speak directly with the group. “It is not safe for our students and it hampers our ability to fulfill our academic mission,” it said. “Please voluntarily leave the library.”

Those gathered outside the library said they were determined to remain until their demands are met, including for the university to cut ties with any company or organization that has business interests in Israel and for the school’s administration to issue a call for a cease-fire in the Israel-Hamas war.

The Portland State University protest is among demonstrations occurring across the nation and at a few Oregon colleges and universities. Several dozen students at Reed College in southeast Portland began occupying a room in Eliot Hall on Monday, a central services building there, a Reed spokesperson said, and have been receiving regular visits from administrators.

At Lewis & Clark College in southwest Portland, there is an outside encampment that a spokesperson for the college described as “peaceful.” In Eugene, The Daily Emerald newspaper reported that about 100 people were gathered at an encampment outside of Knight Library at the University of Oregon.

In Northern California, where protesters occupied two buildings at California State Polytechnic University, Humboldt, dozens of police officers in helmets and carrying batons marched onto campus and cleared both overnight. The university said 25 were arrested and there were no injuries.