PORTLAND, Ore. (AP) — Officials say protesters in Portland, Oregon repeatedly set fire to a police union headquarters building and were repelled by officers spraying tear gas.

A total of 25 people were arrested amid the clashes that lasted into Tuesday morning. Many were charged with interfering with a peace officer and/or disorderly conduct.

Police say in a statement that the protesters in a group of about 300 people hurled rocks and bottles at officers and set three fires to the sides of the Portland Police Association Building and one to an awning. All fires were put out late Monday night and early Tuesday morning.

Among other things, police say the crowd chanted "burn it down." Many in the crowd reportedly carried shields, wore helmets, gas masks, and body armor.

After giving numerous warnings to the protesters, police say they deployed tear gas and used other crowd control munitions to take control of the situation and arrest those who failed to listen to officers.

Portland has been gripped by nightly protests for months since the police killing of George Floyd in Minneapolis.