A US judge has temporarily blocked an attempt by the Trump administration to deport dozens of unaccompanied Guatemalan children back to their home country.

District Court Judge Sparkle Sooknanan's order on Sunday was in response to reports that children had been put onto planes and were about to be sent to Guatemala, where lawyers argued they would be at risk of abuse and persecution.

The children arrived in the US alone and are in government custody while their immigration claims are assessed.

Lawyers for the U.S. Justice Department said the children were not being deported, but rather repatriated so they could be reunited with their families.

The legal proceedings were sparked early on Sunday when immigrant advocacy groups asked for an emergency injunction, claiming around 600 children could be put on planes in Texas and deported.

Judge Sooknanan then issued a temporary restraining order barring officials from sending a group of 10 migrant children between the ages of 10 and 17 to Guatemala.

At a hastily arranged hearing on Sunday afternoon, Judge Sooknanan, who was nominated by former President Joe Biden, expanded the order to cover all unaccompanied children said to be at risk of deportation. The order will be in place for 14 days.

At the hearing, Judge Sooknanan sought assurances from Trump administration lawyers that planes had not already departed with the children on board.

Deputy Assistant Attorney General Drew Ensign said all planes were "on the ground" in the US. He told the judge one plane may have taken off but had returned.

Ensign said the flights were not part of a deportation effort but for family reunifications with parents and other relatives in Guatemala.

He also said the Guatemalan government and the children's relatives had requested the reunifications. Advocacy groups said that was untrue in at least some cases.

In court filings, lawyers for the children argued the action was in violation of federal laws designed to protect children who arrive in the US alone. They said some of the children had pending cases before immigration judges and expressed credible fears about being returned.

"In the dead of night on a holiday weekend, the Trump administration ripped vulnerable, frightened children from their beds and attempted to return them to danger in Guatemala," Efrén C Olivares of the National Immigration Law Center, which filed the suit, said in a statement.

"We are heartened the court prevented this injustice from occurring before hundreds of children suffered irreparable harm."

White House immigration advisor Stephen Miller criticised the judge for blocking the flights.

"The minors have all self-reported that their parents are back home in Guatemala," he wrote on X. "But a Democrat judge is refusing to let them reunify with their parents."

Since the start of his second term, Trump has embarked on sweeping efforts to remove undocumented migrants - a key election promise that drew mass support during this campaign.

In June, the US Supreme Court cleared the way for Trump to resume deportations of migrants to countries other than their homeland without giving them the chance to raise the risks they might face.