The U.S. Supreme Court ordered the Trump administration early Saturday to halt the deportations of at least 30 alleged Venezuelan gang members under the Alien Enemies Act.

“The Government is directed not to remove any member of the putative class of detainees from the United States until further order of this Court,” the order reads.

Two justices, Clarence Thomas and Samuel A. Alito Jr., dissented.

The Trump administration was preparing to deport the Venezuelan men, immigration advocates said Friday as they scrambled to find a federal court they could persuade to step in and block the removals before it was too late.

Attorneys for the detained migrants pressed federal judges in Texas, Washington and New Orleans, as well as the Supreme Court to intervene, arguing that the government had not provided those targeted a meaningful opportunity to challenge the reasons for their removals.

The American Civil Liberties Union said several migrants at an immigration detention center in North Texas had received written notices of removal over the past several days, and a second group of unknown number was told to get ready for travel Friday.

Copies of those notices, filed in court, were written only in English and said the recipient had been “determined to be an Alien Enemy” and would be deported. Aside from stating that the recipient can “make a phone call,” the notices do not inform those who receive them when they will be deported, that they are entitled to contest their removal or outline the means for doing so, the ACLU said.

“There’s no box to check to say I want to contest,” ACLU lawyer Lee Gelernt said during a hastily convened Friday evening hearing in federal court in Washington. “There’s nothing that says there is a right to contest, much less the time frame.”

Justice Department lawyer Drew Ensign told the court that the government had no plans to fly any of the targeted migrants out of the country Friday night but “reserve[d] the right” to begin them as soon as Saturday.

He maintained that officials need only provide 24 hours’ notice to targeted individuals and were not required to instruct them on how to contest deportation decisions. As of Friday evening, there were no known flights officially scheduled for Saturday, Ensign said.

Trump’s use of the Alien Enemies Act, a rarely invoked wartime statute, is at the center of an escalating standoff between his administration and the courts that is bringing the nation closer to a constitutional standoff. His administration deported more than 130 Venezuelans under the Alien Enemies Act on March 15. The government has since sent two more flights carrying migrants to El Salvador, but none of those men were deported under the wartime authority.

The Supreme Court ruled this month that the Trump administration had the authority to deport migrants under the act but said the government must first provide detainees an opportunity to contest their removals. Those challenges, the justices said, should be brought in the court districts nearest to the detention centers where the migrants are being held. That set off a flurry of activity in federal courts across the country as immigration advocates seek to locate and identify migrants targeted for removal and quickly file individual cases on their behalf in front of multiple federal courts.

In a Friday court filing, the ACLU said that “officers last night told class members that they will be removed within 24 hours … upon information and belief, individuals have already been loaded on to buses.”

A spokeswoman for the Department of Homeland Security declined to respond to a request for comment on the ACLU’s claims in its filings. “We are not going to reveal the details of counter terrorism operations, but we are complying with the Supreme Court’s ruling,” Tricia McLaughlin said in an email statement.

Chief U.S. District Judge James E. Boasberg of Washington, D.C., denied the ACLU’s request for a temporary restraining order, even as he described the notice as “very troubling.”

“I strongly doubt that the notice, particularly with a short time frame, complies with the Supreme Court instruction, where it doesn’t give anything about the right to challenge or seek a hearing,” Boasberg said. But the judge said he no longer had jurisdiction to intervene and that the matter was up to the U.S. Court of Appeals for the 5th Circuit and Supreme Court, where the ACLU had also filed pending requests.

Judge James Wesley Hendrix of the U.S. District Court for the Northern District of Texas on Thursday denied an initial request for a temporary restraining order, concluding that based on the government’s statements, the two men identified by their initials in that case did not face “imminent risk” of removal because the government said it had “no present plans to remove either petitioner” until the case was resolved and that it would tell the court if that changed. Hendrix denied the ACLU’s request to meet Friday, citing the appeal to the 5th Circuit.

At the Supreme Court, ACLU lawyers told the justices that numerous Venezuelan migrants currently in government custody in Texas are “in imminent and ongoing jeopardy of being removed from the United States without notice or an opportunity to be heard,” in direct conflict with the Supreme Court’s April 7 order.

They urged the justices to quickly intervene, saying many individuals had already been loaded onto buses presumably headed to the airport and have been informed that they might be removed from the United States as soon as Friday afternoon or Saturday.

The lawyers requested an immediate order from the Supreme Court barring any removals and said that without this court’s intervention, dozens or hundreds of proposed class members “may be removed to a possible life sentence in El Salvador with no real opportunity to contest their designation or removal.” The “lightning-fast timeline,” the lawyers said, does not give individuals seeking to join the class-action lawsuit a “realistic opportunity to contest their removal” under the Alien Enemies Act.

Boasberg temporarily blocked the administration from using the Alien Enemies Act for deportations as the first flights to El Salvador were in the air in March. Boasberg announced in an order this week that he has found probable cause that Trump administration officials willfully violated his order not to remove Venezuelan migrants from the country based the Alien Enemies Act, and he has launched a criminal contempt inquiry. The federal appeals court for Washington Friday put on hold Boasberg’s decision pending its review.

Ann Marimow contributed to this report.