More demonstrators were arrested Monday as classes resumed at the University of California, Los Angeles, the site of some of the tensest moments during a wave of student activism at U.S. universities over the war in Gaza.

Lieutenant Richard Davis of the U.C.L.A. campus police said 43 people were arrested in a campus parking deck on misdemeanor charges of conspiracy to attempt burglary. The arrests came as pro-Palestinian demonstrators attempted a sit-in at Moore Hall, student organizers said.

About 30 protesters were sitting in a corner of the parking deck around 9:45 a.m. local time, with their hands zip tied behind them. They were later taken to a sheriff’s bus.

The university sent a message telling students and faculty members to avoid Moore Hall and switched to remote classes.

Another group of demonstrators amassed in nearby Dodd Hall, where about 40 were inside on Monday morning, chanting, “Disclose, divest, we will not stop, we will not rest.”

U.C.L.A. administrators originally took a tolerant approach to a pro-Palestinian encampment at the school, even as student protesters were arrested across the nation. But the peace was shattered late Tuesday: Videos analyzed by The New York Times showed pro-Israeli counterprotesters attacking students in the encampment, beating them with sticks, using chemical sprays and launching fireworks as weapons.

No arrests have been made in connection with the attack, which the police allowed to continue for hours without intervention. But on Thursday, police officers from three law enforcement agencies arrested more than 200 pro-Palestinian demonstrators and dismantled their camp.

The university said on Sunday that it had created a new campus safety position as it examines what led to clashes between demonstrators there.