Seven police officers were injured and at least 30 people were arrested at Portland State University on Thursday after anti-Israel agitators occupied the library on campus, according to Portland police.

The department said the arrests stem from the agitators illegally entering Millar Library for a second time despite efforts by authorities to keep it secure after initially clearing it at 9:30 a.m. local time on Thursday.

The operation began at 6 a.m. when Portland police officers from all three precincts established a perimeter around the library and began telling the occupiers to leave. After “numerous announcements” with no success, officers moved into the building and began a “deliberate, methodical and safety-focused clearing” beginning on the top floor, police said.

On that floor, police found barricades, vandalism and items “staged for potential assault” on the officers working to clear the building, though they were not met with resistance by the agitators, the department said.

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When officers reached the first floor, the department said they found a “heavily barricaded door” that required the strength of several people to open it. Behind the door, the floors were “coated with paint and soap, or some other slippery substance.” 

Four people were arrested, including one who deployed a fire extinguisher at an officer and another who tried to hit an officer with an improvised shield. Portland police said the remaining occupiers fled the area after being warned repeatedly they would be arrested for trespassing.

While moving those arrested into a transport van, a “hostile crowd surrounded the van” and the Oregon State Police Mobile Response Team was called for help leaving the area, Portland police said, adding that “some uses of force” were necessary.

The crowd followed the van to the Interstate 405 freeway and some protesters even got on the freeway, which led to additional arrests.

While some officers did carry “40mm less-lethal launchers with orange shoulder straps,” only pepper spray was deployed to gain control of the situation. 

“These tools are standard and issued to patrol officers who have been trained and qualified in their use. Their use is regulated by PPB use of force policy, but again no munitions were deployed,” the department said.

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After the library was cleared Thursday morning, the university attempted to secure it with plywood and a fence, but the agitators tore it down and re-entered the building, prompting officers to return to campus.

Seven more people were arrested by Portland police and one person was arrested by PSU Campus Safety.

“It is important to remember that although arrests are not always made at the scene, when tensions are high, this does not mean that people are not being charged with crimes later,” Portland police said, adding that cases will be forwarded to the Multnomah County District Attorney for prosecution.

At the end of the day, Portland police said seven officers were injured during the operation on campus – the most serious being a knee injury that required transport to the hospital. 

The remaining six officers experienced minor injuries or were still being assessed when the statement was released Friday morning.