Customs agents in Philadelphia say they found 8 grams (0.28 ounces) of heroin stuffed inside a congratulatory greeting card shipped from the Netherlands.

The front of the card, written in Dutch, read, "Success!"

Officials said Monday the card was addressed to someone in Washington, D.C. So far, no one has been arrested.

The value of the heroin was estimated at $500. It was found in a plastic bag sandwiched between two pieces of cardboard.