Updated 6:20 p.m. Eastern Time
Authorities intercepted a parcel this morning addressed to Rep. Peter King (R-N.Y.) containing a bloody pig's foot and a derogatory message, a source has confirmed to CBS News.
The parcel was intercepted at the Congressional mail facility in Landover, Maryland, where mail sent to lawmakers is screened for security risks.
The U.S. Capitol Police and U.S. Postal Service confirmed that there is an open investigation, though would not confirm the details of what was contained in the parcel because the investigation is ongoing. King's office, which did not see the parcel, referred all questions to the Capitol Police.
According to the Postal Service, a hazardous materials response team tested the parcel and found it to be non-hazardous.
Last month, King heldthat critics suggested unfairly targeted Muslims, though it's not known whether this incident is related to those hearings. Muslims are forbidden from eating pork products.
Ibrahim Hooper, National Communications Director for the Council on American-Islamic Relations - a target of King's hearings - said he found the situation confusing. He said his organization regularly receives pig-themed hate messages, including letters smeared with bacon.
"My guess is it was an anti-Muslim bigot, and bigots not being brain surgeons they probably got their signals crossed," he said.
UPDATE: A source on Capitol Hill told NBC News that the note "contained anti-Semitic ramblings" and referenced the radicalization hearings. King is Roman Catholic.