Veteran NFL quarterback Peyton Manning was adamant in his denial over using performance-enhancing drugs after he was referenced in an Al Jazeera report in December, but the story doesn't appear to be going away any time soon and as the Denver Broncos star prepares for Super Bowl 50. According to The Associated Press on Wednesday, the NFL began investigating the reports week ago about a shipment of human-growth hormones (HGH) to Manning's wife in Florida.

The Al Jazeera report stated that the Guyer Institute, an anti-aging clinic in Indianapolis, sent the drugs to Manning's wife, Ashley, and while Manning was a member of the Indianapolis Colts. Al Jazeera posted an online documentary entitled “The Dark Side: Secrets of the Sports Dopers,” in which Charlie Sly, a former intern at the clinic, claimed the Manning’s received HGH. The report has since been dismissed by Manning, other players accused of using PEDs and by Sly himself.

Brian McCarthy, vice-president of communications for the NFL, stated that "the inquiry involves reviews of records, interviews and coordination with other agencies," according to the AP report.

Manning had missed the entire 2011 season with the Colts after undergoing four neck surgeries. The following season, Manning signed with Denver and picked up where he left off as one of the best quarterbacks in the NFL. The 39-year-old reached the Pro Bowl in 2012, 2013 and 2014, but some believe that the upcoming Super Bowl will be the final game of his illustrious career as injuries and age have limited his performance.

Manning has not denied that his wife received shipments of HGH, and admits he went to the Guyer clinic to use a hyperbaric chamber during his recovery. But he has been steadfast in his denial of ever using a performance-enhancing substance.

"Absolutely not, absolutely not," Manning told ESPN’s Lisa Salters. "What hurts me the most about this, whoever this guy is, this slapstick trying to insinuate that in 2011, when more than less I had a broken neck -- I had four neck surgeries. ... It stings me whoever this guy is to insinuate that I cut corners, I broke NFL rules in order to get healthy. It's a joke. It's a freaking joke."

In an interview on the "Today" show in December, Al Jazeera reporter Deborah Davies denied that the documentary accused Manning of using a banned substance.

"First of all, let's make it clear what the allegation is," Davies said. "The allegation in the program is very simple: that when Charlie Sly worked in the Guyer during part of his training, his rotation for pharmacy, the clinic was sending out not one shipment, but repeated shipments of growth hormone to Ashely Manning in Florida. That's it. That's the allegation."

Dale Guyer of the Guyer Institute claims that Sly was an unpaid intern there in 2013, long after Manning ever visited the clinic, while Davies stated that Sly was doing his PHD in pharmacy and was doing his rotation. Sly has backed up that claim, saying his statements were false and Al Jazeera recorded him without his consent.

“To be clear: I am recanting any such statements and there is no truth to any statement of mine that Al Jazeera plans to air,” Sly said in a video posted on YouTube. "Under no circumstances should any of those statements, recordings or communications be aired.”

On Thursday, Manning reaffirmed to reporters after practice that he supports an investigation.

"I do welcome it. It's no news to me," Manning said. "I still stand by what I said then that it's garbage from the first day that it came out, garbage today."

Much of the media has dismissed the report. ESPN’s Mike Ditka said that Al Jazeera was “spreading garbage,” and CBS play-by-play broadcaster Jim Nantz has said he wouldn’t talk about the allegations during game broadcasts because it is a “non-story” on “all levels.”

CBS will broadcast the Super Bowl, which will be played on Sunday, Feb. 7.