WASHINGTON (AP) — A Republican congressman is asking the Obama administration to explain delays in its arrest of a registered sex offender who was living in the U.S. illegally and working as an unpaid intern for a Democratic senator.

The Associated Press reported this week that the Homeland Security Department had instructed federal agents not to arrest 18-year-old Luis Abrahan Sanchez Zavaletahim, who was working in the office of Democratic Sen. Robert Menendez of New Jersey. Republican Congressman Jason Chaffetz of Utah called the situation "disturbing" in a letter to Homeland Security Secretary Janet Napolitano.

The department said there were no instructions to delay arresting Sanchez and said it followed standard procedures.

Chaffetz wants to know who ordered immigration agents not to arrest Sanchez until after the election, and why.