Pro-Palestinian protesters briefly disrupted a graduation ceremony at the University of Michigan in the United States, on Saturday, while demonstrators clashed with police at the University of Virginia, as American universities braced for more unrest during graduation ceremonies.

Across the United States, students are gathering or setting up tents on dozens of universities to protest the months-long war in Gaza and to demand that President Joe Biden, who supports Israel, do more to stop the bloodshed in Gaza. They also demand that their universities withdraw their investments from companies that support the Israeli government, such as arms supply companies.

Video clips circulated on social media showed dozens of students wearing the traditional Palestinian keffiyeh and graduation caps and waving Palestinian flags as they walked in the middle aisle of Michigan Stadium in Ann Arbor, amid cheers and boos from a crowd estimated at thousands.

The party continued and campus police escorted the demonstrators toward the back of the stadium, but no arrests were made, according to Colleen Mastoni, university spokeswoman.

Mastoni said in a statement, “Peaceful protests like these have occurred at University of Michigan graduation ceremonies for decades. The university supports freedom of opinion and expression, and university leaders are pleased that today’s graduation ceremony was a moment of pride and triumph.”

The weekend witnessed more events on American universities, as views on the Israeli war in Gaza varied, and sometimes violently, over the past two weeks.

Several universities, including Columbia University in New York City, called in the police to quell the protests.

The University of Virginia in Charlottesville again witnessed tensions for a short period, on Saturday. Riot police officers could be seen in a video moving into a camp of pro-Palestinian demonstrators, handcuffing some demonstrators with plastic handcuffs and dragging them across the grass.

So far, police have arrested more than 2,000 demonstrators from universities across the country.

The University of Michigan is one of several universities that have changed their security protocols for graduation ceremonies.

The university told Reuters last week that it had trained employee volunteers on how to mitigate disturbances, a change from the usual duties of guiding guests around campus and to their seats.