Sen. Bob Menendez (D-N.J.). (AP)

Sen. Bob Menendez (D-N.J.) is pushing back hard against reports that his office employed an unpaid intern who was a registered sex offender and in the country illegally, saying his office had no idea of the intern’s past criminal history.

A report published Wednesday afternoon by The Associated Press said that the Department of Homeland Security instructed federal agents not to arrest the intern, Luis Abrahan Sanchez Zavaleta, 18, until after Election Day. Menendez handily won reelection in November, defeating state Sen. Joseph Kyrillos (R).

Sanchez, an immigrant from Peru, was arrested by Immigration and Customs Enforcement agents on Dec. 6, according to the AP report.

Menendez’s office appeared blindsided by the report, not issuing a lengthy explanation of the situation until late Wednesday.

“Luis Sanchez was an unpaid college intern in our Newark office for approximately 2 months,” Menendez communications director Tricia Enright said in an e-mailed statement. “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. Clearly Mr. Sanchez sought to deceive our staff.

“Upon notification from authorities of his arrest, Mr. Sanchez’s relationship with our office immediately ended,” Enwright added. “Senator Menendez was briefed on the situation today – and he is appalled. He has no tolerance for those who violate the law and expects the authorities to continue to prosecute the case.”

In an interview with MSNBC on Wednesday afternoon, Menendez said he had only just heard of the situation and that his staff learned about 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.

DHS officials also pushed back strongly against the AP report. Though the department doesn’t comment on individual arrests, DHS spokesman Peter Boogaard called the story “categorically false,” saying that ICE “followed standard process in coordination with its federal partners and local prosecutors before taking appropriate enforcement action.”

The case hits especially close to home for Menendez, who remains a vocal advocate for overhauling the nation’s immigration laws. In his MSNBC interview, Menendez said Sanchez’s arrest “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.”

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