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."

President Joe Biden addressed the nation on Thursday saying that free speech and the rule of law must both be upheld.

"We are not an authoritarian nation where we silence people or squash dissent, the American people are heard. In fact, peaceful protest is the best tradition of how Americans respond to controversial issues," Biden said, speaking from the White House.

But, he condemned the destruction of property, shutting down campuses and forcing the cancelation of classes and graduation, saying it isn't peaceful protest.

"Dissent is essential to democracy, but dissent must never lead to disorder or to denying the rights of others so students can finish the semester and their college education," Biden said.

Biden last commented on college protests on April 22 -- before there was an escalation of suspension and arrests at campuses across the country -- at the time condemning antisemitic actions and those who don't understand the plight of Palestinians in Gaza, a message he reiterated Thursday.

"There is no place for hate speech or violence of any kind whether it's anti-Semitism, islamophobia or discrimination against Arab Americans or Palestinian Americans. It’s simply wrong. There’s no place for racism in America," Biden said.