Unidentified federal agents dressed in camouflage are driving around Portland, Oregon, in unmarked minivans and grabbing protesters off the street, according to local reports. Oregon Public Broadcasting reports that the mysterious officers have been using unmarked vehicles to patrol the city and detain protesters since July 14, when they were first spotted. Videos posted online show the officers driving up to people, taking people into their vans with no explanation, and driving away. Protesters Mark Pettibone and Conner O’Shea told OPB that one van pulled up in front of them in the early hours of Wednesday. “I see guys in camo,” O’Shea said. “Four or five of them pop out, open the door and it was just like, ‘Oh shit. I don’t know who you are or what you want with us.’” Pettibone was arrested but later released. According to OPB, federal officers have charged over a dozen people with crimes related to the protests so far. The U.S. Marshals Service refused to comment on the use of unmarked vehicles.