A renowned pro-Palestine Columbia University student was detained by US federal immigration authorities claiming to be operating on behalf of the Department of Homeland Security (DHS).

Mahmoud Khalil, a recent Columbia University graduate who helped lead last year's Gaza Strip solidarity marches, was detained on Saturday in his university-owned apartment building near Columbia's Manhattan campus in New York City.

US law requires federal authorities to acquire an arrest warrant before entering non-public university areas, including residential buildings.

Following his detention, Khalil called his lawyer, Amy Greer, to intervene by phone. She questioned the two plainclothes immigration officers about why her client was being arrested and if they had an arrest warrant, while also informing them that Khalil was a green card holder. 

"He has a green card," one agent, perplexed by the finding, informed his boss over the phone. However, a second later, the agent reported that the State Department had "revoked that too."

A State Department spokeswoman stated that they have extensive jurisdiction to cancel visas under the Immigration and Nationality Act.

The agency "exercise[s] that authority when information comes to light at any time indicating that a visa holder may be inadmissible to the United States or otherwise ineligible for a visa," according to a spokesperson.

Khalil, who is Palestinian, was initially kept in custody at the Immigration and Customs Enforcement (ICE) office in downtown New York. However, his counsel stated that he was sent to the Elizabeth Contract Detention Facility in New Jersey.

Greer stated to reporters, "We have not been able to get any more details about why he is being detained," adding that this was a "clear escalation."

Khalil's detention comes as US President Donald Trump pledges to deport international students and punish "agitators" who protest the Israeli occupation's actions. 

During last year's rally, Khalil was one of Columbia's most conspicuous pro-Palestinian activists. As students put up tents on campus last spring, Khalil was chosen to act as a negotiator on their behalf, meeting with university administration regularly.

"The administration is following through on its threats," Khalil's lawyer told reporters.

Columbia University probes students for criticizing 'Israel'

Columbia University has launched multiple investigations, spearheaded by the newly established Office of Institutional Equity, to track down students who have voiced criticism of "Israel", according to records obtained by The Associated Press.

In recent weeks, the university has issued notices to dozens of students for actions ranging from sharing pro-Palestinian social media posts to participating in what the school deems "unauthorized" protests.

The creation of this "disciplinary office" has sparked concerns among students, faculty, and free speech advocates, who argue that the university is caving to pressure from Trump, who has threatened to cut federal funding to universities and deport campus "agitators".

Several students and faculty members told AP that they were accused of attending protests they never participated in or sharing social media posts they never authored.

Moreover, US federal authorities announced on Friday a cut in grants and contracts with Columbia University in New York, citing pro-Palestine protests, which the Trump administration labels as "anti-semitic".