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."

After police and protesters clashed on the campus of the University of Texas at Austin following a dispersal order, leading to some arrests on Monday, the school issued a statement, saying it "took swift action to preserve a safe, conducive learning environment for our 53,000 students as they prepare for final exams."

"UT Austin requested backup assistance from the Texas Department of Public Safety to protect the safety of the campus community and enforce our Institutional Rules, such as the rule that prohibits encampments on campus. Because of the encampments and other violations of the University’s Institutional Rules related to protests, protestors were told repeatedly to disperse. When they refused to disperse, some arrests were made for trespassing. Others were arrested for disorderly conduct," the university's statement read.

UTA said protests since the start of the Israel-Hamas war have happened "largely without incident."

"The University strongly supports the free speech and assembly rights of our community and we want students and others on campus to know that protests on campus are fully permissible, provided that they do not violate Institutional Rules or threaten the safety of our campus community," the statement concluded.

-ABC News' Marilyn Heck