(CNN) Federal officials on Monday ordered protesters occupying an encampment to leave the grounds of a US Immigration and Customs Enforcement field office in Portland or face arrest.

But officials didn't give a deadline for the eviction order of the Occupy ICE PDX demonstrators.

Last week, ICE temporarily closed its Portland field offices after demonstrators had pitched tents in front of the facility to protest the Trump administration's "zero tolerance" policy. The encampment is one of several Occupy ICE movements that have emerged in various cities.

Fascist DHS terrorists handing out flyers telling us what we're doing is illegal. pic.twitter.com/t0bnHE4IMV — Abolish I.C.E PDX (@OccupyICEPDX) June 25, 2018

Early Monday, federal officials entered the Portland building to secure items and equipment, and remained in the building. Hours later, officers with the Federal Protective Service distributed notices to the demonstrators, ordering them to vacate the property, according to Billy J. Williams, US attorney for the District of Oregon.

According to Williams' office, it's illegal to obstruct entrances, lobbies, offices and parking lots of federal buildings, like one in southwest Portland.

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