WASHINGTON – Another top official is leaving the Department of Homeland Security, paving the way for President Donald Trump to install his preferred choice to head the agency.

Claire Grady, the department's undersecretary of management and the second in line to lead, has offered her resignation, effective Wednesday, according to outgoing DHS Secretary Kirstjen Nielsen. The departure continues Trump's purge of high-ranking officials at the massive Department of Homeland Security.

In addition to requesting Sunday's resignation of Nielsen, Trump and aides forced the removal of Secret Service Director Randolph "Tex" Alles.

Grady's departure will remove a bureaucratic issue that emerged when Trump sought Nielsen's resignation. In announcing Nielsen's departure, Trump also said Kevin McAleenan – the commissioner of Customs and Border Protection – would become the department's acting secretary.

The statute that governs DHS, however, mandates that the department's under secretary of management – Grady – take over as acting secretary in the event of a departure by the secretary.

Nielsen, who announced Grady's departure over Twitter on Tuesday evening, said Grady had served both the Defense Department and Homeland Security for 28 years with "excellence and distinction."

"She has been an invaluable asset to DHS – a steady force and a knowledgeable voice," Nielsen said. "Her sound leadership and effective oversight have impacted every DHS office and employee and made us stronger as a Department."

The Trump administration is also reportedly examining the removal of additional DHS officials in what many have characterized a "purge" within the department. They include Lee Cissna, director of United States Citizenship and Immigration Services, his policy director, Kathy Nuebel Kovarik, and John Mitnick, the department's general counsel.

Last week, Trump withdrew the nomination of Ronald D. Vitiello, the acting director of Immigration and Customs Services (ICE), to do the job full time.

"We're going in a little different direction," Trump said on Friday. "Ron's a good man. But we're going in a tougher direction."

A change in leadership:Homeland Security Secretary Kirstjen Nielsen resigns amid migrant surge at US-Mexico border

More:Who is Kevin McAleenan, Trump's acting homeland security chief after Kirstjen Nielsen leaves?

A number of media reports have said White House adviser Stephen Miller is driving the shakeup within the DHS and encouraging Trump's desire to appoint people who will apply "tougher" immigration policies.

The most senior Republican member of the Senate issued a rare public warning to Trump over the changes, saying the president might be "pulling the rug out from the very people that are trying to help him" when it comes to achieving his immigration goals.

Iowa Sen. Chuck Grassley told Fox News on Monday that "it would be a real mistake" to "fire good people like that," referring to the list of additional officials who could be ousted in the shakeup. Grassley told The Washington Post that he was "very, very concerned."

Contributing: William Cummings, USA TODAY

More:Grassley warns Trump may be 'pulling the rug out' from those helping him on immigration

White House departures:Who's been fired and who resigned