Portland State University reopened its campus Friday, a day after police removed pro-Palestinian protesters who had been holed up in the university’s main library for several days.

Police from the city of Portland and the university arrested 31 people throughout Thursday — starting with 12 people, including four students, as they cleared Millar Library in the morning, and then more throughout the day as crowds of onlookers waxed and waned for hours near the building, ending with eight arrests in the evening after a small group returned.

During the big sweep of the library, police arrested three people inside, including one who they said deployed a fire extinguisher against them. The rest of the occupiers fled the library. One of them tried to hit an officer with a shield and was arrested, police said.

A “hostile” crowd surrounded a police van carrying suspects as it tried to leave the campus Thursday morning, and the crowd then followed the van, prompting more arrests, police said.

Portland State University work crews put up a fence around the library after police left Thursday morning. In the early evening, some people returned, tore down the fence and broke into the library again, police said. Officers returned and, in the ensuing police operation, made eight more arrests. One of those arrests was made by a Portland State University officer.

Police said they detained the driver of a white Toyota Camry who briefly accelerated toward a crowd of pro-Palestinian demonstrators and then ran off spraying what appeared to be pepper spray toward protesters who confronted him.

The man was taken to a hospital on a police mental health hold, the Portland Police Bureau said in a written statement late Thursday afternoon. They did not release his name.

People screamed as the vehicle accelerated toward the crowd, but the driver braked before it reached anyone. Demonstrators quickly approached the car and began striking it, and the driver exited and sprinted off while aiming the spray toward those trying to catch him. Police said they found him later and took him into custody.

Demonstrators badly damaged the car, smashing in windows and spray painting graffiti on it.

Portland Police released a list of everyone arrested during the operations Thursday, including their names, age and the charges they could face. Those arrested ranged in age from 18 to 60, according to the list. Most faced a charge of second-degree trespassing, a misdemeanor. Other charges included resisting arrest, third-degree escape and burglary. At least six of those arrested were students, Portland Police said.

Portland State University reopened the campus Friday morning. The library, however, remains closed.

“The occupiers not only extensively vandalized the exterior and interior walls, but they stole some of our valuable collection and equipment,” PSU President Ann Cudd said in a statement.

A spokesperson for the university wouldn’t confirm which pieces of the library’s collections are missing, saying in an email that it will “take quite a while” to catalog the extent of what was damaged or stolen.

Friday morning, police caution tape cordoned off the library as Portland Police officers stood by their cruisers on the northeast and southeast ends of the library and work crews removed graffiti from the walls. There were no protesters in the area.