IN THEIR BOLDEST action here yet, illegal-immigrant activists sat down and blocked traffic in front of the federal immigration office at 16th and Callowhill streets yesterday, demanding the release of a man who is in detention and chanting for their human rights.

Two women were arrested when they refused to get up after being allowed to sit in the middle of 16th Street for nearly an hour, their legs crossed atop banners that read "Undocumented Unafraid" and "Coming Out of the Shadows," as traffic was diverted with about 100 supporters around them.

Jessica Hyejin Lee, 20, a Bryn Mawr College junior, and Tania Chairez, 19, a sophomore at the University of Pennsylvania's Wharton School, continued pumping their fists in the air as Capt. Bill Fisher of the police Civil Affairs Unit gave them the last of three warnings.

They were taken to Central Detectives, 21st and Hamilton streets, and placed in a holding cell while waiting to be processed. A detective said last night that they were expected to be charged with obstruction of the highway, a misdemeanor.

Chairez, who had written about her undocumented status in the Daily Pennsylvanian in October, was brought to this country by her parents from their native Mexico when she was 5. They first lived in Phoenix.

Lee was brought to the U.S. from South Korea by her parents in 2003; they overstayed tourist visas. She came out publicly about her undocumented status at a Bryn Mawr event last year in front of a packed auditorium.

During the sit-down, when the crowd of supporters - a mix of undocumented and legal residents - chanted slogans including "Out of the shadows, into the streets!" and "Education, not deportation," no one from U.S. Immigration and Customs Enforcement came out to talk with the protesters.

People in the building - which also houses the U.S. Citizenship and Immigration Services - peered out of windows.

Before the sit-down, Lee and Chairez went into the federal building, through security, and walked to an information window to hand a letter to Thomas Decker, the field-office director for ICE's enforcement and removal operations. They were not able to meet with him personally.

Their letter demanded the release of Miguel Angel Orellana Garcia, 25. Orellana had been living in Bucks County with his U.S.-citizen girlfriend, with whom he has two sons, one age 4 and the other born during Orellana's detainment in York County Prison, where he has been since July.

Orellana had been brought into the U.S. illegally as a child by his parents from El Salvador and was later arrested and pleaded guilty to minor drug and alcohol charges.

After Chairez and Lee left the building without having been detained, Chairez said she planned to sit in the street until they got a response about Orellana. But no response ever came.

The rally was part of a series of protests coordinated by the National Immigrant Youth Alliance during a "Coming Out of the Shadows" week for illegal immigrants.

The rally began at LOVE Park, where Cesar Marroquin, 21, said that for illegal immigrants like himself, "the more out we are, the safer we are." He said that people who have been open about their status "have this whole network behind you if you get caught by ICE."

He added: "ICE doesn't want that bad look on them - that they're deporting the youth."

In front of the LOVE statue, Chairez, Lee and three other people spoke of how they each were brought to this country as children and later found out they were here illegally. The others who spoke were Edith Ramirez, 17, and Karla Rojas, 17, both from Mexico; and Gabriela Alfaro, 19, from Costa Rica.