A chaotic scene unfolded Saturday night in downtown Portland, as a protest devolved into a riot, police said.

Protesters blocked the streets, throwing bottles and other projectiles at officers and attacking a news crew. Some dragged metal barricades onto MAX train tracks, prompting transit officials to urge people to avoid traveling downtown.

At least 19 people were arrested late Saturday night, police tweeted.

At one point, officers located and removed as stockpile of bricks and rocks near Pioneer Courthouse Square.

Protesters initially met at Pioneer Courthouse Square at 6 p.m. Saturday night before beginning their march at around 6:45 p.m. The group of a couple hundred protesters was much smaller than the throngs of thousands that had shown up previous nights.

Police described the demonstration as an "unpermitted protest march."

Protesters organized in New York, Los Angeles, Washington, D.C., and other cities for the fourth night of protests across the country and the fifth night of protests in Portland. A mostly peaceful protest in Indianapolis turned violent toward then end when a couple of protesters clashed with police.

Contributing: Steph Solis, USA TODAY.