After a group claimed responsibility on Monday for setting fire to at least 15 police cars at the Portland Police Bureau’s training facility, Portland officials along with the FBI and U.S. Attorney’s Office spoke Wednesday about last week’s protest-related vandalism in the city.

The group is called “Rachel Corrie’s Ghost Brigade” and they claim that they set fire to the police cars because they knew officers were going to sweep the Portland State University library to clear out pro-Palestinian protesters who were occupying the building, KPTV reports.

The group posted their claims on social media, saying they cut through a fence at the training facility and set 10 fires, which spread to 15 police cars.

Portland Fire & Rescue and Portland police officers responded to the fires last week early Thursday morning. It was the same morning police moved into the Millar Library to clear out protesters at PSU.

The fires were to police training vehicles that are only used for training purposes. Police say after the arson, other neighboring agencies have offered their vehicles for the department to use.