LOS ANGELES, California (X17online) - The federal investigation into Heath Ledger's death has been closed, and the DEA subpoena against Mary-Kate Olsen 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 According to a government official, the subpoena is no longer valid because it was contingent upon prosecutors pursuing the case; however, the case could be brought back if evidence of a crime surfaces.

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

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