Performances in Portland have not subsided for more than three months.
Police arrested 15 other people in Portland during protests outside a police station on Sunday night.
The protesters set fire to mattresses that were eventually extinguished by firefighters, Portland police said in a statement.
According to police, there were no injuries. Fifteen people were arrested on charges of resisting law enforcement officers, hooliganism, possession of dangerous devices, and arson.
On Saturday, Portland police arrested 59 people and fired tear gas when protesters began throwing rocks and firebombs at officers.
For more than three months, protests have been taking place in Portland every night, sometimes resulting in violent clashes between demonstrators and police, as well as between right-and left-wing groups.
Demonstrations began across the country after an African-American man, George Floyd, died in custody in May.