By Makini Brice and Jonathan Allen

WASHINGTON/NEW YORK (Reuters) – The acting head of the U.S. Department of Homeland Security has ordered an investigation into reports that border patrol agents have been posting offensive anti-immigrant comments and threats against lawmakers on a private Facebook group.

The move was announced amid mounting criticism of the Trump administration’s handling of a humanitarian crisis along the U.S.-Mexico border, with lawmakers and government investigators warning of dangerous conditions in migrant detention centers.

“Reporting this week highlighted disturbing and inexcusable social media activity that allegedly includes active Border Patrol personnel,” acting DHS head Kevin McAleenan said on Twitter on Wednesday, calling the reported comments “completely unacceptable.”

He said any employee found to have “compromised the public’s trust in our law enforcement mission will be held accountable.”

The Facebook posts, first reported by the non-profit news site ProPublica included jokes about the deaths of migrants and sexually explicit content referring to U.S. Representative Alexandria Ocasio-Cortez, a Democrat who was highly critical of the detention facilities after a tour this week.

The White House also criticized a ruling by a federal judge in Seattle who on Tuesday blocked an administration move to keep thousands of asylum seekers in custody while they pursued their cases.

“The district court’s injunction is at war with the rule of law,” White House press secretary Stephanie Grisham said in a statement. “The decision only incentivizes smugglers and traffickers, which will lead to the further overwhelming of our immigration system by illegal aliens.”

The American Civil Liberties Union and other immigrant rights groups sued the government in April after Attorney General William Barr concluded that asylum seekers who entered the country illegally were not eligible for bond.

U.S. District Judge Marsha Pechman on Tuesday ruled that people detained after entering the country to seek asylum were entitled to bond hearings.

MIGRATION FLOWS

The record surge of mostly Central American families at the U.S. southwestern border has begun to ease after tougher enforcement efforts in Mexico, although the situation remains dire, according to Mexican and U.S. officials.

The U.S. government’s internal watchdog on Tuesday said migrant-holding centers in Texas’ Rio Grande Valley were dangerously overcrowded, publishing graphic pictures of cells holding twice as many people as they were built for.

Mexico’s government, citing unpublished U.S. data, said migrant arrests at the border fell 30% in June from the previous month after it started a migration crackdown as part of a deal with the United States to avoid possible trade tariffs.

The Mexican government said it was now busing home dozens of Central American migrants from Ciudad Juarez, across the border from El Paso, Texas, who were forced to wait in Mexico for their asylum claims to be processed under a U.S. policy known as “Remain in Mexico.”

“Mexico’s effort to control the flow of migrants appears to have broken a growing trend,” the country’s foreign ministry said in a statement.

After migrant arrests reached a 13-year monthly high in May, immigration has arguably become the biggest issue for President Donald Trump and the Democratic contenders vying for the chance to face him in the 2020 presidential election.

U.S. Senator Cory Booker would “virtually eliminate immigration detention” if he wins the White House, his campaign said on Tuesday.

Presidential hopeful Julian Castro last week proposed decriminalizing border crossings as a step toward freeing up federal resources and eliminating thousands of cases clogging criminal courts – an initiative favored by Senator Elizabeth Warren, who is also running for the Democratic nomination.

Trump, meanwhile, looked to stir up support for his policies, promising immigration raids after the July 4 U.S. holiday to arrest migrants with deportation orders.

(Reporting by Daina Beth Solomon, Diego Ore and David Alire Garcia in Mexico City, Jonathan Allen in New York and David Alexander and Makini Brice in Washington; Writing by Andrew Hay and Paul Simao; Editing by Michael Perry and Bill Trott)