Updated 3 p.m.

Federal law enforcement officers on Monday notified demonstrators camped outside Portland's Immigration and Customs Enforcement headquarters that they must begin to vacate federal property.

"It is unlawful under federal law to obstruct the entrances, foyers, lobbies, corridors, offices and/or parking lots of federal facilities," reads the flyer Federal Protective Service agents distributed to protesters, who have blockaded the Southwest Macadam Avenue facility since last week.

Those who obstruct the entrance to the building, according to the flyer, face arrest and prosecution in federal court. However, officials acknowledged they had no authority over adjacent properties owned by other entities.

Activists have waged the round-the-clock occupation in opposition to the Trump administration's immigration crackdown, including its policy of separating migrant children from their parents at the U.S. border.

ICE officials suspended its operations at the building last Tuesday as the so-called Occupy ICE PDX movement grew in size.

The order to abandon camp comes hours after federal law enforcement agents entered the ICE building in the middle of the night to "secure government property," according to news release sent to media just after 3:30 a.m.

It may also lead to a showdown between federal authorities and a band of unwavering activists whose week-long protest has generated national headlines and inspired other demonstrations outside of ICE facilities around the country.

The tent community was mostly quiet through early Monday afternoon. Interspersed through tents lining the railroad tracks are places meant to serve different purposes: a quiet tent with a stocked bookshelf, a family tent for children filled with colorful toys, a pantry, a makeshift shower, an engineering tent, a medical station and a dishwashing station.

"There's something prophetic about this place," said Rabbi Ariel Stone, of Congregation Shir Tikvah in east Portland, who came out to support the encampment Monday morning. "The word of God comes most clearly from people who are crying out for justice."

Edith Gillis, 60, of Portland stood outside the main entrance waving at passersby with a sign around her neck that read, "Protect protesters who protect Portlanders."

Gillis, who said she's been joining the protest every day since the first Sunday, said as a Christian, taxpayer and mother, she disagrees with ICE immigration policy.

"Some sacrifice everything for their kids' safety and well-being only to be worse off," she said. "I've experienced that trauma."

Last week, Portland Mayor Ted Wheeler lambasted ICE in a series of tweets and announced he will not have city police break up the protest at the federal agency's Southwest Portland field office. A spokeswoman on Monday said Wheeler's stance hadn't changed and that Portland police won't be responding.

Wheeler is traveling Monday, the spokeswoman said, and isn't in Portland. City Commissioner Chloe Eudaly, however, visited the camp and expressed her support for the protesters.

Chloe Eudaly at Occupy ICE PDX Portland city commissioner Chloe Eudaly is visiting the Occupy ICE PDX camp in southwest Portland. Posted by The Oregonian on Monday, June 25, 2018

Billy J. Williams, U.S. Attorney for the District of Oregon, said on Monday his office will be working to support ICE and Federal Protective Service agents.

"While demonstrators have a lawful right to assemble and voice their concerns, blocking the building's driveways or entrances is not permitted under federal law," Williams wrote in a news release.

This report will be updated.

— The Oregonian/OregonLive

Shane Dixon Kavanaugh, Anna Spoerre, Gordon R. Friedman and Jim Ryan of The Oregonian/OregonLive staff contributed to this report.