As San Francisco began imposing its first night of an 8 p.m. citywide curfew, SFPD officers made around 80 arrests, many of them for violating that curfew.

"Demonstrations in San Francisco were overwhelmingly orderly and peaceful today, and SFPD officers were proud to help facilitate these in a way that protected the First Amendment rights and safety of all who took part," said SFPD Chief Bill Scott in a statement Sunday evening. But nonetheless after the curfew took effect, demonstrators were still gathered outside City Hall and the assembly was declared unlawful. As KPIX reports, the majority of those arrested were likely cited and released quickly.

But not all the arrests were for peaceful activities.

"At this time, SFPD has made approximately 80 arrests in the Market Street, SOMA and Union Square areas for violations of the curfew order or looting,” Scott said. “Some of these arrests resulted in the seizure of a firearm and explosives."

Police followed a group of activists/anarchists who were walking in the vicinity of Market and Second Street after 8 p.m., throwing what were described as Molotov cocktails. Police Commander Teresa Ewins tells KPIX that there were five individuals committing acts of arson and vandalism. "There was a huge explosion and fire came out of a tub because of something they threw in there,” Ewins tells the station. “It’s pretty shocking people would do that…all the way down [the street] there were about four more explosions."

One of the individuals' backpacks was seized and found to contain M80s, fireworks, and Molotov cocktails, according to police.

According to a fire department scanner, four people were arrested at the scene near Market and Second.

Another individual was found carrying a semi-automatic handgun with an extended magazine — which is illegal in California — in a backpack in the vicinity of the 300 block of Sutter Street, as the SFPD tweeted from the scene.

As the Mercury News reports, curfews have now been imposed in San Jose, Danville, and Walnut Creek, but not in Oakland, where Mayor Libby Schaaf has nonetheless encouraged residents to stay home.

Mayor London Breed has extended the 8 p.m. curfew indefinitely in San Francisco. And she expressed frustration Sunday both with activists coming to yell at her outside her Lower Haight apartment the previous evening, and with others who were moving around the city intent on vandalism and looting.

"I was extremely upset because unfortunately with some of the vandals, they thought this was a game, they thought this was funny," she said.

She also said that the fire department had been "inundated with calls about fires that were deliberately set" on Saturday, some "with Molotov cocktails that were thrown and ignited fires."

Fortunately no large blazes were caused.

Related: Thousands Again Protest Through San Francisco; Groups Gather at Union Square, City Hall