Heath Ledger maryheath1.jpg

Mary-Kate Olsen must have breathed a sigh of relief today when she learned that the federal investigation into Heath Ledger's death was closed, and that the DEA subpoena against her will not be enforced.

The Associated Press reports that prosecutors have called off the case "because they don't believe there's a viable target." According to a government official, the subpoena is no longer valid because it was contingent upon prosecutors pursuing the case; however, the case could be brought back if evidence of a crime surfaces.

As you may recall, Mary-Kate's masseuse, Diana Wolozin, was the one who discovered Heath's body in his New York City home on January 22, 2008. Wolozin phoned Mary-Kate before calling 911, which raised questions as to what involvement, if any, the 22-year-old actress had in Heath's death.