(Reuters) - Green Bay linebackers Clay Matthews and Julius Peppers, along with Pittsburgh's James Harrison, have been cleared by the National Football League of any link to performance-enhancing drugs, the league said on Wednesday.

In a statement, the NFL said it had found "no credible evidence" that the players were provided with or used substances prohibited under the league's policy on performance-enhancing substances.

All three players met with NFL investigators last week regarding allegations of doping made in a documentary by Al-Jazeera America in December.

"Initiated in January, the investigation was led by the NFL's security and legal teams with support from expert consultants and other professionals," the league said.

"The investigation involved witness interviews, a review of relevant records and other materials, electronic research, and laboratory analysis and review."

Al-Jazeera had reported that an unpaid former intern pharmacist told an undercover reporter that the players, along with free agent Mike Neal and since-retired quarterback Peyton Manning, were supplied with performance-enhancing drugs.

In July, the NFL cleared Manning of wrongdoing but that league has yet to announce details of its investigation of Neal.

The Guyer Institute intern pharmacist, Charlie Sly, later recanted his statement but the NFL continued its investigation into the report before issuing its statement on Wednesday.

(Reporting by Mark Lamport-Stokes in Los Angeles; Editing by Frank Pingue)