Sen. Robert Menendez (D-N.J.) holds a news conference with leaders from Latino legal organizations in the LBJ Room at the U.S. Captiol, Aug. 5, 2009 in Washington, D.C. (Chip Somodevilla -- Getty Images)

The AP reports that Sen. Robert Menendez (D-N.J.) employed as an unpaid intern a registered sex offender who was in the country illegally, and that the Department of Homeland Security told federal agents not to arrest the teenager until after Election Day. 

Luis Abrahan Sanchez Zavaleta, an 18-year-old immigrant from Peru, was arrested by U.S. Immigration and Customs Enforcement agents in front of his home in New Jersey on Dec. 6, two federal officials said. Sanchez, who entered the country on a now-expired visitor visa from Peru, is facing 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.

The Homeland Security Department disputes the AP's report that the arrest was delayed until after the election. 

"The report is categorically false," DHS spokesman Peter Boogaard said in a statement. "ICE followed standard process in coordination with its federal partners and local prosecutors before taking appropriate enforcement action.” 

Menendez's office says they knew nothing about Sanchez's background; he was intern in the Newark office for about two months.

"No staff member responsible for managing the internship program had reason to believe, based on their interview process, that Sanchez had any criminal background or immigration issues," spokeswoman Tricia Enright said in a statement. "Senator Menendez was briefed on the situation today - and he is appalled." 

Menendez was elected to a second term in November, easily beating state Sen. Joseph Kyrillos (R). 

In an interview with MSNBC on Wednesday afternoon, Menendez said he had only just heard of the situation. 

"I didn't know anything about this young man's status until right before I came on this program," the senator said. His staff, he said, learned of the issue on Monday.

"There's no way we could know about his status," Menendez told MSNBC. "There's no way we could know about his background" as a sex offender, he added, because Sanchez was a juvenile when the offenses occured. 

The senator was initially booked to discuss immigration reform, coincidentally. He brought the arrest back to that topic, "It does speak volumes about why we need comprehensive immigration reform, because we can't know who is here to pursue the American dream versus who is here to do it damage," he said.