ESPN has pulled out of a collaboration with PBS’s “Frontline” program just as an investigative film about the NFL and player concussions was to air.

“Frontline” said Thursday that ESPN has withdrawn its involvement on “League of Denial: The NFL’s Concussion Crisis,” a documentary about the NFL’s response to head injuries among players. The sports network, which has a lucrative deal to broadcast NFL games, will no longer permit “Frontline” to use its logos nor other credits on the two-hour film, nor two “Frontline” Web sites related to it. The film is scheduled to air in October on PBS stations.

“We don’t normally comment on investigative projects in progress, but we regret ESPN’s decision to end a collaboration that has spanned the last 15 months,” wrote “Frontline” executive producer David Fanning and Raney Aronson, deputy executive producer, on the “Frontline” Web site late Thursday.

“League of Denial” is based on reporting by “Frontline” and two ESPN journalists, Mark Fainaru-Wada and Steve Fainaru, a former Washington Post reporter. The Fainaru brothers are the authors of a forthcoming book, also titled “League of Denial.” They will continue to work on the TV documentary and will appear in it, “Frontline” said.

The title and trailer for the film portray it is a hard-hitting indictment of the NFL’s handling of head injuries.

The league was sued earlier this month by 83 former players, including former Washington Redskins running back Clinton Portis, over claims that the NFL didn’t do enough to protect players from head trauma and covered up evidence of the long-term impact of brain injuries. A separate lawsuit that makes similar claims was filed in June on behalf of hundreds of former players. The NFL repeatedly has denied the claims.

ESPN broadcasts “Monday Night Football” under a multibillion dollar contract with the NFL. But ESPN spokesman Josh Krulewitz said the network’s withdrawal from the Frontline project was unrelated to its agreements with the league.

“This is not an issue of us backing off” a controversial topic, Krulewitz said. Instead, he said, “We had no editorial control [over the PBS documentary] and weren’t comfortable lending our branding to it. . . . In hindsight we should have reached this conclusion much sooner, and that was a mistake on our part. Obviously, it’s a strange situation.”

Both Krulewitz and “Frontline” producers said ESPN executives haven’t seen the documentary, which is still in production.

ESPN, and ESPN the Magazine have produced multiple stories about the concussion issue since 2006.

On Sunday, the cable network’s investigative program, “Outside the Lines,” carried a story that raised more questions about Elliot Pellman, a Long Island rheumatologist with no previous expertise in brain research who served as chairman of the league’s research arm. The story reported on Pellman’s role in discrediting independent research into brain trauma and his involvement in studies that played down the impact of concussions.

The story, produced in conjunction with “Frontline,” was a follow-up to a 2006 report in ESPN the Magazine on Pellman’s research record. That story found that Pellman’s committee concluded that returning to play after a concussion “does not involve significant risk of a second injury either in the same game or during the season” and that there is “no evidence of worsening injury or chronic cumulative effects of multiple [brain injuries] in NFL players.” The magazine profile led to Pellman’s dismissal as chairman of the NFL committee.