Portland police say that at least 30 people have been arrested over their involvement in ongoing protests at Portland State University.

"Additional arrests have been made at PSU’s library after trespassers illegally entered the building again despite efforts to secure it," police said in their statement. "Preliminary count is 30 arrests over the course of the day. Officers will continue to monitor for criminal activity and will make arrests when lawful and appropriate."

Authorities say that officers encountered acts of vandalism, and one suspect deployed a fire extinguisher at an officer during an altercation.

"Seven officers suffered injuries, the most serious was a knee injury that required ambulance transport to the hospital. Other injuries are still being assessed or were minor," Portland police said.

The identities of those arrested will be released once a full list has been completed.

USC has sent an email to the arrested protesters on Thursday evening warning that any student protesters who have been arrested for their "alleged conduct" of criminal trespassing on April 24 will be “referred to the University’s disciplinary process.”

"Please be aware that any further violation of university policies - including but not limited to the university's policies against camping, amplified sound, defying DPS directives, vandalism, harassments, bullying, and theft of property - will result in further discipline up to expulsion as well as an immediate ban from campus," the email obtained by ABC News said.

The Portland Police Bureau announced seven additional arrests were made Thursday evening amid ongoing protests at Portland State University.

The seven arrests came a couple of hours after PPB announced 22 people had been arrested on Thursday, bringing the total to 29 people arrested on Thursday.

PPB said the seven arrests were from "trespassers" breaking "back into the library" by pulling the fence down.

"Arrests have also been made for people refusing to leave the park block at the library," the bureau said in an update on X late Thursday evening.

The Portland Police Bureau said 22 arrests have been made amid the ongoing protests at Portland State University.

"PPB has arrested a total of 22 people during the events on the PSU campus," the bureau said in an update on X Thursday.

Earlier in the day, Oregon Gov. Tina Kotek released a statement condemning vandalism reported at the PSU Library.

“I fully condemn the criminal actions taken Thursday morning that resulted in the burning of 15 Portland Police Bureau cars, endangering first responders and the surrounding community," Kotek said, adding, "This includes the acts of vandalism seen this week at the Portland State University library and against nearby businesses."

Columbia University has threatened student protesters with "clear consequences" after protesters occupied a building in an escalating standoff. Students defied a 2 p.m. deadline to disperse Monday.

Students occupying the building face expulsion, the university warned.

"We made it very clear yesterday that the work of the University cannot be endlessly interrupted by protesters who violate the rules. Continuing to do so will be met with clear consequences. Protesters have chosen to escalate to an untenable situation—vandalizing property, breaking doors and windows, and blockading entrances—and we are following through with the consequences we outlined yesterday," Columbia said in a statement.

Students who did not commit to the terms Columbia's proposed agreement to vacate the encampment by 2 p.m. Monday have been suspended.

"Those students will be restricted from all academic and recreational spaces and may only access their individual residence. Seniors will be ineligible to graduate," Columbia said.

"This is about responding to the actions of the protesters, not their cause," Columbia said.