In the morning, a woman was arrested at the encampment outside City Hall after she set another person’s clothes on fire, police said. In another incident hours later, a woman was arrested after protesters said she struck a man with a tent pole. Both were booked on suspicion of assault with a deadly weapon.

Also Friday, police arrested a man on suspicion of climbing a tree and dumping fluorescent paint on a historic marble fountain that the city barricaded earlier this week to protect from vandalism.

The incidents are distressing, city officials say, because up until now protesters at Occupy Los Angeles have been mostly peaceful.

“We have not seen violent incidents like this,” Los Angeles Police Department Cmdr. Andrew Smith said. “But two felonies from the south lawn in one day? This has raised concerns for us.”