A Republican congressman asked the Obama administration Friday why the arrest of a registered sex offender who was living illegally in the United States and working for Democratic New Jersey Sen. Robert Menendez was delayed for weeks.

U.S. Rep. Jason Chaffetz (R., Utah), chairman of a House oversight subcommittee on homeland defense, asked the Homeland Security Department whether politics played any role in the decision not to arrest Luis Abrahan Sánchez Zavaletahim, 18, until after the Nov. 6 election.

The Associated Press reported this week that the department ordered immigration agents not to arrest Sánchez, an unpaid intern working for Menendez, until after Election Day. The department said it did not order such a delay and said it followed standard procedures. Menendez advocates aggressively for pro-immigration policies and was reelected in November with 58 percent of the vote.

Chaffetz called the situation "disturbing" in a letter dated Thursday to Homeland Security Secretary Janet Napolitano. He asked officials to brief him and his staff by Jan. 3 and provide answers in writing.

Authorities in Hudson County notified U.S. Immigration and Customs Enforcement agents in early October that they suspected Sánchez was an illegal immigrant who was a registered sex offender and who might be eligible for deportation. ICE agents in New Jersey notified superiors at Homeland Security because they considered it a potentially high-profile arrest, and the department instructed them not to arrest Sánchez until after the election, one U.S. official told the AP. ICE officials complained that the delay was inappropriate, but the department directed them several times not to act, the official said.

ICE agents arrested Sánchez on Dec. 6 in front of his home in New Jersey, two federal officials said. Sánchez, who entered the country on a now-expired visitor visa from Peru, faces deportation and remains in custody.

The officials spoke on condition of anonymity because they were not authorized to discuss details of Sanchez's immigration case. Menendez said that his staff learned of this on Dec. 10, but that he personally found out about the case through the AP's reporting.

During the final weeks of President George W. Bush's administration, ICE was criticized for delaying the arrest of then-President-elect Barack Obama's aunt, who had ignored an immigration judge's order to leave the country several years earlier after her asylum claim was denied. She subsequently won the right to stay in the United States.