The arrests came hours after St. Anthony, Minnesota, police officer Jeronimo Yanez was found not guilty on Friday of second-degree manslaughter in 32-year-old Castile's July 2016 shooting death in the St. Paul suburb of Falcon Heights.
The shooting drew national attention after the victim's girlfriend live-streamed the bloody aftermath on social media and it led to protests that have fueled debate across the country over police use of force in encounters with minorities.
Protesters held a peaceful demonstration on Friday at the Minnesota State Capitol in St. Paul and then about 1,500 converged on Interstate 94 in the city, blocking the freeway, a Minnesota State Patrol spokeswoman said in an email statement.
Authorities repeatedly asked protesters to leave before making 18 arrests shortly after midnight on Saturday, the email statement said. Charges against them are pending for unlawful assembly and other charges, it said.
Among those listed as arrested for alleged unlawful assembly were at least two journalists.
Yanez, the son of a Mexican immigrant, testified during the trial in Ramsey County District Court that he feared for his life after Castile began reaching for a firearm that Castile had disclosed he had in his possession.Read more at Reuters