A encampment with the Occupy ICE movement is grown in front of Portland's U.S. Immigration and Customs Enforcement field offices.
Don Ryan/AP
A encampment with the Occupy ICE movement is grown in front of Portland's U.S. Immigration and Customs Enforcement field offices.
(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.

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.

CNN affiliate KOIN reported that protestors covered a surveillance camera with their notices and blocked a set of doors on Monday.

In a Facebook post Monday, Occupy ICE PDX – PDX is the airport code for Portland – pledged resistance.

“We anticipated that ICE would use invasive and opaque tactics to deter the movement that is spreading across the nation. ICE can try us here in Portland, but we are unrelenting,” the post said. “Rooted as a tree, solid as a rock, united as a people. We are organized, we are ready, we here to stay until ICE is abolished!!! We need you to Rise Up, Fight Back!”

Occupy ICE movements have popped up in various cities, including New York City, Los Angeles and Detroit in opposition to President Trump’s policy to criminally prosecute anyone who crosses the border illegally, instead of referring those with children to immigration courts, much like previous administrations had largely done.

The policy led to many children being separated from their parents because children can’t be held in federal prisons with adults facing prosecution.

In Detroit, protestors temporarily shut down operations at the local ICE office on Monday – their third day of a week-long protest at the ICE office, CNN affiliate WXYZ reported.

Detroit police broke up the protest and forced protestors to vacate the federal property, the station reported.

“We want to support their right to do that, but they have to follow the rules and regulations we have in the city of Detroit,” said police Capt. Kurt Worboys told the station.

After criticism, the President changed course last week and signed an executive order aimed at keeping some families together at the border.

More than 2,000 children who have been separated from their families still await reunions with their parents.

The Department of Homeland Security released a plan for putting back together the thousands of families on Saturday night, but the reunions have been slow.

Protests have erupted again along the US-Mexico border despite the President’s pledge to reunite immigrant children with their parents.

CNN’s Nicole Chavez and Chris Boyette contributed to this report.