The U.S. Postal Service intercepted a package Monday containing a severed pig's foot and an anti-Semitic note addressed to Rep. Pete King, R-N.Y., the chairman of the House Homeland Security Committee, sources tell Fox News.

The package had a return address, but it was unclear if the address was random, Lorrie McCallister, a U.S. Postal inspector, said. The investigation is ongoing.

A spokesman from King's office in Washington D.C. says Capitol Police have opened an investigation into the matter.

"The package never got to the office," Kevin Fogarty, King's chief of staff, said. "All congressional mail is screened before it gets here."

Fogarty said King's office is cooperating with the investigation.

McCallister said proper protocols were followed and when workers discovered the package, a hazardous materials team was called in to investigate.

In March, King held high-profile congressional hearings on Islamic radicalization in the U.S., saying he aimed to confront the threat of homegrown extremism.

The controversial hearings were applauded by some for addressing the issue while criticized by others, including one Democrat who accused King, who is Catholic, of "scapegoating" the entire religion of Islam.

Further details about the intercepted package weren't immediately available. King's office declined to comment when contacted Monday evening.

There will not be any changes in mail delivery to King's Washington office.

Fox News' Chad Pergram and Edmund DeMarche contributed to this report.