SAN FRANCISCO — Viral videos of riot police repeatedly pepper spraying a row of seated, nonviolent Occupy Wall Street protesters at a California university have sparked outrage, an investigation and calls for the college chancellor’s resignation.

It also set off a debate about how far officers can and should go to disperse peaceful demonstrators.

While many students, lawmakers and even the university’s chancellor saw the officers’ actions as excessive, some experts on police tactics say, depending on the circumstances, pepper spray can be a less violent crowd-control measure than dragging protesters away or swinging at them with truncheons.

“Between verbalized commands and knock-down, drag-out fights, there’s quite a bit of wiggle room,” said David Klinger, a former Los Angeles Police Department officer and instructor at the University of Missouri-St. Louis who reviewed the pepper spray footage.

“When you’ve got a bunch of people who are clearly noncompliant, locking arms, it doesn’t look good (on camera),” he said.

Soon after the incident Friday at the University of California, Davis, video recordings spread across the Internet.

The footage of an officer casually spraying an orange cloud over protesters while spectators screamed in horror joined other much-discussed pepper-spray incidents, such as the 84-year-old activist hit in the face in Seattle and a Portland, Ore., woman who recently was sprayed in the mouth.

The university said Monday that it has placed the police chief and two officers on administrative leave to restore trust and calm.

Still, nearly 2,000 students and residents gathered at the main quad to hear speeches and chant slogans against police and university officials. Students who were pepper-sprayed opened the protest, saying they felt unsafe on campus with the chancellor in power.

“We were just kids sitting down in a circle singing,” said student David Buscho, 22, of San Rafael, Calif. “It felt like hot glass … I was paralyzed with fear.”

Pepper spray derives its active ingredient from chili peppers. When the spray is deployed, it causes inflammation, resulting in dilation of the capillaries in the eyes, paralysis of the larynx and a burning sensation on the skin.

Buscho said students were yelling at police Friday that they were peacefully protesting.

One of the helmeted officers began pointing a spray can directly at protesters’ faces, he said.

“I had my arms around my girlfriend. I just kissed her on the forehead and then he sprayed us,” he said. “Immediately, we were blinded … He just sprayed us again and again and we were completely powerless to do anything.”

The protest was held in support of the overall Occupy Wall Street movement and in solidarity with protesters at the University of California, Berkeley who were struck by police with batons Nov. 9.

The UC Davis footage shows two officers spraying students in the face with the chemical agent as the crowd cries out, then a slight delay before police start hauling off some of those seated while other protesters cough violently and try to crawl away.

The spray the officers used ranked about halfway between the highest and lowest concentrations of the commercially available substance.

Nine UC Davis students hit by pepper spray were treated at the scene, and two were taken to hospitals and later released, university officials said. Ten people were arrested.

Students and faculty have called for the resignation of UC Davis Chancellor Linda Katehi.

“I’m here to apologize,” she told the crowd. “I really feel horrible for what happened on Friday.”