SAN FRANCISCO/TIJUANA (Reuters) - Two people from Central America seeking asylum in the United States were sent back across the border to Mexico on Thursday, despite their claims that a return to Mexico was too dangerous, as part of the first test of a controversial new Trump administration policy.

FILE PHOTO: Migrants from Central America are seen escorted by U.S. Customs and Border Protection (CBP) officials after crossing the border from Mexico to surrender to the officials in El Paso, Texas, U.S., in this pictured taken from Ciudad Juarez, Mexico December 3, 2018. REUTERS/Jose Luis Gonzalez/File Photo

The returns came as a U.S. federal judge in San Francisco on Friday heard legal arguments on whether or not to halt the policy, known as the Migrant Protection Protocols (MPP), which was rolled out in late January.

The major policy shift is based on a decades-old law that says migrants who enter from a contiguous country can be returned there to wait as their deportation cases move forward. But this provision had never been used for these types of returns before.

The American Civil Liberties Union and other rights groups have sued, saying that migrants are being returned to dangerous border towns where they cannot access legal counsel or get proper notice of their hearings.

Two migrants from Honduras tried to make the case to U.S. asylum officers that Mexico was too dangerous for their return, according to their lawyer Robyn Barnard from the nonprofit group Human Rights First. But on Thursday evening, after being held in custody for two days, they were sent back across the border.

A third migrant, 35-year-old Douglas Oviedo from Honduras, said he was interviewed by authorities and returned to Tijuana on Tuesday. They are among the first to test the process of claiming a fear of returning to Mexico.

Asylum seekers typically undergo what is known as a “credible fear” interview to assess their eligibility for a court process. But the standard of proof for a “reasonable fear” of being returned to Mexico is much stiffer.

Barnard said one client, 19-year-old Ariel, who asked to be identified only by his middle name, broke down in tears during the interview with U.S. officials, which lasted several hours.

Another client, a 29-year-old man who said he was an evangelical leader who fled Honduras because of threats over his anti-gang activity, was also sent back, Barnard said.

More than 200 people have been returned to Mexico so far under the MPP, which is now in place at the San Ysidro and Calexico ports of entry in California and the El Paso, Texas, port of entry and to migrants who ask for asylum between ports of entry in the San Diego area, according to the U.S. Department of Homeland Security (DHS).

That is a small portion of the tens of thousands of migrants mostly from Central American who have tried to enter the United States and claim asylum in recent months.

The U.S. government has said the policy is necessary to stem the ballooning number of asylum claims, many of which are ultimately denied, because migrants can end up living in the United States for years due to huge immigration court backlogs.

DHS did not immediately respond to a request for comment on their cases. The U.S. Citizenship and Immigration Services, which conducts asylum interviews said it cannot comment on individual cases because confidentiality rules apply.

“A lot is still unknown, I haven’t been given any written reasons or determinations for their return,” Barnard said.

Lawyers for the rights groups and for the government argued over the technical aspects of the policy on Friday in front of U.S. District Judge Richard Seeborg. He asked a series of detailed questions about whether the Trump administration had discretion to implement the policy. Seeborg also wondered how broadly of an injunction he could issue and whether any stop to the policy should apply nationally. He is expected to rule on the case in a written decision.