PORTLAND, ORE. >> Fires set outside a law enforcement building that’s a frequent site for protests in Portland, Oregon, prompted police to declare a riot early Saturday and detain several demonstrators.

Witnesses also said a car drove near the demonstration at the Portland Police Association building and fired several gunshots into the air. Video posted online showed shell casings in the street. No injuries were reported.

Officers had extinguished the fire at the police building and appeared to detain several protesters. It was unclear how many were arrested.

The commotion followed a sit-in in the lobby of the Portland mayor’s condo building Friday night. Protesters have issued demands, including police budget reductions and Mayor Ted Wheeler’s resignation, the Oregonian/OregonLive reported. A crowd of about 150 had gathered outside the building.

Portland has been gripped by nightly protests for three months since the police killing of George Floyd in Minneapolis. The demonstrations, often violent, usually target police buildings and federal buildings. Some protesters have called for reductions in police budgets while the city’s mayor and some in the Black community have decried the violence, saying it’s counterproductive.

Seventy-four people are now facing federal charges related to protests that have rocked the city for three months since George Floyd was killed, the local U.S. attorney announced Thursday.

The misdemeanor and felony charges include assaults on federal officers, arson and damaging federal property.

Earlier Friday, Wheeler had said he sent a letter to President Donald Trump declining his offers to help the city manage the protests. In early July, Trump sent more federal agents to the city to protect the federal courthouse, but local officials said their presence made things worse. The federal agents later pulled back.