Originally Published: 22 JUL 21 09:00 ET

By Priscilla Alvarez, CNN

(CNN) -- Democratic Sen. Ron Wyden of Oregon will not advance President Joe Biden's pick to lead US Customs and Border Protection until he receives more answers about the agency's role in the Portland unrest last year, delaying a key nominee as the administration reevaluates border restrictions.

"Six months into the new administration, the Departments of Homeland Security and Justice have failed to answer basic questions about how the Trump administration misused federal resources to stoke violence against peaceful protesters in my hometown," Wyden said in a statement.

Wyden, who chairs the Senate Finance Committee, said he's unable to advance the nomination of Tucson, Arizona, Police Chief Chris Magnus to serve as Customs and Border Protection commissioner "until DHS and DOJ give Oregonians some straight answers about what they were up to in Portland last year, and who was responsible." The committee has jurisdiction over the Customs and Border Protection commissioner.

The delay forced by Wyden means that Customs and Border Protection, which was confronted with an increase of migrants at the US-Mexico border this year that led to overcrowded facilities and unaccompanied children staying in custody for extended periods, will continue to be led by acting leadership for the foreseeable future. The agency is also charged with implementing an array of border restrictions linked to the coronavirus pandemic.

Tensions grew in Portland last summer after federal officers arrived in the city, which had experienced prolonged and at times violent protests over demands for racial justice and police accountability. A DHS inspector general report released this year found that the department had surged hundreds of federal agents to Portland with incomplete training and missing equipment.

At the time, Wyden had sought answers from then-Attorney General William Barr and former acting Homeland Security Secretary Chad Wolf about the deployment of federal officers, calling the response on the ground "intolerable."

After Biden took office, Wyden followed up his previous requests for information in a pair of June letters to Homeland Security Secretary Alejandro Mayorkas and Attorney General Merrick Garland, reiterating his concerns about the lack of adequate training and on-the-ground coordination among agencies. The questions are similar to those first raised last year but remain unanswered, according to Wyden, who cited some previous responses in his letters.

"The White House was notified on June 11 of what was needed to have a hearing on Magnus. As they have not provided it, Sen. Wyden informed the administration this week he would not be able to hold a hearing until his questions are sufficiently answered," a Wyden aide said.

Customs and Border Protection, currently helmed by acting Commissioner Troy Miller, is one of the three immigration agencies under DHS operating with acting leadership, until those selected to lead are confirmed by the Senate. It's become familiar territory for each agency after rotating leadership under Trump. Immigration and Customs Enforcement, which is currently led by career official Tae Johnson, never had a Senate-confirmed director during the four years of the Trump administration.

Last Thursday, Biden's pick for ICE director, Ed Gonzalez, testified before the Senate Homeland Security Committee, in a step toward possible confirmation. Gonzalez, who was elected sheriff of Harris County, Texas, in 2016, has a decades-long career in law enforcement, according to his biography.

Ur Jaddou, who was selected to serve as US Citizenship and Immigration Services director, also already had her hearing before the Senate Judiciary Committee and was voted on favorably. She's now on the Senate executive calendar. Jaddou was chief counsel at the agency under President Barack Obama and led the Biden-Harris DHS transition review team.

Still missing on the calendar is Magnus, whose nomination is now stalled.