Federal immigration officials are taking dramatic steps to comply with a court order involving President Barack Obama’s executive action on immigration, including knocking on doors of immigrants and warning that their protection from deportation will be cut off by month’s end.

The problem for the Obama administration escalated earlier this month, when U.S. District Judge Andrew Hanen demanded that Homeland Security Secretary Jeh Johnson and other top immigration officials appear in his Brownsville, Texas, courtroom to explain why they shouldn’t be held in contempt of court.

The Department of Homeland Security, which is overseeing implementation of Obama’s immigration actions, had mistakenly issued three-year work permits to immigrants protected from deportation – even after the February injunction from Hanen that blocked such documents.

About 2,500 such work permits have been issued, and Christopher Bentley, a spokesman for U.S. Citizenship and Immigration Services – an agency under DHS – said officials have retrieved roughly 900 of the documents.

But according to a July 14 DHS memo from Johnson filed in court on Wednesday, immigration authorities are employing aggressive maneuvers to get the rest of the work permits back and to avoid having Johnson and other top administration officials held in contempt.

Government officials are working to ensure that the three-year work permits mistakenly received by the immigrants are changed to two years. But by Friday, USCIS officials plan to contact the immigrants who haven’t yet returned their three-year work permits to warn them that their protection from deportation and ability to work will end altogether by July 31 if they haven’t returned the three-year documents, according to Johnson’s memo.

These immigrants are generally those who were brought to the United States illegally as children but protected under a 2012 Obama directive, which was vastly expanded with the president’s November 2014 executive actions.

In addition to telephone calls and snail mail, U.S. Citizenship and Immigration Services is sending employees to homes of these immigrants to get the work permits back.

Johnson wrote that agency personnel “shall do this at a reasonable hour, and in a respectful and appropriate manner.” Still, immigration advocacy groups, who are helping the Obama administration retrieve the work documents, expressed concerns.

“The USCIS home visits unfortunately will add to the mounting confusion and anxiety communities feel as they await a resolution in the executive action case,” said Vanessa Esparza-López, supervising attorney for the National Immigrant Justice Center’s Immigrant Legal Defense Project. “But individuals should know it is critical to comply with requests to exchange their work permits, whether they receive a letter or visit at their homes.”

The National Korean American Service & Education Consortium, another advocacy group that has focused on immigration, said in a statement Thursday that the home visits were likely to concentrate on immigrants in Los Angeles, Chicago, Dallas, Houston, and San Francisco.

The mess over the incorrectly issued permits has been a side storyline to the main court case, which has indefinitely blocked Obama’s immigration actions announced last fall that could protect more than 4 million immigrants here illegally from deportation and give them the ability to work. The Fifth Circuit Court of Appeals heard oral arguments in the broader legal case last week.