Police have arrested four people on the second day of Martin Luther King Jr. marches in Oakland.

The march originated Sunday evening in the downtown area and progressed toward a transit station, said a police spokeswoman, who said that officers helped facilitate that march, according to an Associated Press report.

Four people were ultimately arrested on charges of assaulting a police officer. Another 17 received citations for a number of different violations.

Police also arrested four on Saturday during mostly peaceful demonstration that was part of the MLK marches.

The marches are part of a series of events planned throughout the Bay area over the holiday weekend to honor Martin Luther King Jr., and they are also being used to protest the deaths of black men at the hands of police in Ferguson, Missouri and in New York.

The demonstrations shut down Fruitvale BART station for a short period of time. The station reopened at around 10:20 p.m., according to a Bay City News report.

Demonstrators gathered at Frank Ogawa Plaza at around 7 p.m. and began their march through Oakland about half an hour later. The demonstrators were reportedly protesting police tactics during the march.

USA Today reported that about 150 protesters blocked traffic and shouted anti-police slogans as dozens of polie followed them on foot and on motorcycles. While the demonstrations were largely peaceful, there were some tense stand-offs between police in riot gear and protesters along the route.

Protesters earlier had demonstrated at a Walmart store partly for Martin Luther King day and in opposition to racism and police violence. About 50 protesters conducted a “die-in” outside the Walmart, and 100 people disrupted shoppers at a shopping center near Oakland.