San Francisco police officers raided 888 Turk Street, a building Occupy SF protesters took over earlier this year.
SFPD is asking building owners to board up, fence in and do just about anything to keep Occupy demonstrators from taking over their empty building, according to the San Francisco Examiner.
The warning comes as authorities anticipate an impending takeover of an undisclosed property on May 1.
This wouldn't be the first time Occupy protesters have seized vacant buildings in the city. Earlier this month, police arrested 75 people for taking over a Turk Street structure which is owned by the Archdiocese of San Francisco.
Police say graffiti was smeared on walls inside. And back in January, 20 demonstrators were arrested for taking over the shut down Cathedral Hill Hotel. One nearby business was vandalized.
Some occupy protesters say the take overs are meant to send a message to city leaders about the lack of housing for those in need. They also want to bring to attention how people are being lured by predatory loans.