The NFL has found "no credible evidence" that James Harrison, Clay Matthews and Julius Peppers used or were provided with prohibited substances after an investigation into allegations made in a documentary by Al-Jazeera.

An NFL statement said the investigation, which started in January, "involved witness interviews, a review of relevant records and other materials, electronic research, and laboratory analysis and review.''

After the interviews last week, a source close to the situation told ESPN that the players were not confronted with any new evidence or allegations.

The league interviewed Peyton Manning, who also was named in the report, earlier this offseason and issued a statement last month clearing his name.