(CNN) -- Current and former Auburn University officials -- including two ex-football coaches -- are forcefully challenging news reports that allege improprieties during the Tigers' 2010 national championship run.
In both instances -- first to a story that broke Wednesday claiming players received money and had failing grades changed to passing, then to a story that asserted players failed drug tests for synthetic marijuana -- the Alabama school denied the allegations as "baseless" and "inaccurate.
The university's athletics department issued a statement accompanied by an "open letter" from Athletic Director Jay Jacobs specifically about a story reported Thursday by ESPN.
The sports network claimed that a dozen members of the Auburn football team that won the 2010 BCS title failed tests for synthetic marijuana. As many as a dozen other senior players on the team used the substance known as "spice" but were never caught, the report alleges.
ESPN reported its "six-month investigation ... reveals" the number of positive tests and synthetic marijuana users, though it does not specify the source for the figures it cites.
The story posted online alludes to interviews with two former players, one of their lawyers and one of their mothers.
The players are among four kicked off the Auburn team in March 2011 after being arrested after an alleged armed robbery. Multiple news organizations, including al.com, reported all four were later indicted on burglary, robbery and theft of property charges. They all denied the charges. One of them, Antonio Goodwin, has been convicted and sentenced through 2027, according to the Alabama Department of Corrections, while the others are awaiting trial.
In addition to the interviews, the ESPN report also refers to courtroom testimony in Goodwin's trial from onetime star running back Michael Dyer, as well as text messages between one of the arrested players and his father.
ESPN said the athletic program kept the failed tests confidential.
Hours after the ESPN report came out, Auburn responded with a critical statement and Jacobs' letter.
"After a thorough internal review, the Auburn Athletics Department believes many of the allegations made by the individuals interviewed for this story are baseless and inaccurate," the university said.
In its response, the school athletics department said it didn't begin testing for synthetic marijuana until "a test became available" at the end of January 2011 -- a few weeks after the Tigers defeated Oregon in the national championship game.
Its policy was amended in March 2011, with the official addition of synthetic marijuana as a banned substance under the athletic department's drug testing program.
Since that time, the school said there have been three positive tests -- out of 2,500 drug tests administered -- among its student-athletes.
The Auburn response alluded to the former players cited by ESPN. The story cites one of arrested players' lawyers, Davis Whittelsey, as saying he'll argue in court that Auburn was more concerned with covering up drug tests than getting students drug counseling.
Auburn strongly rejects that assertion.
"As a father of three, I sympathize with the parents of the young men who face prison sentences for their alleged involvement in the armed robbery," Jacobs wrote, referring to players quoted in the ESPN article. "While they have a right to speak out, I have an obligation to share the facts, which clearly show Auburn athletics tried to help these former student-athletes."
The athletic director singles out a comment to ESPN from one ex-player -- Goodwin, who was interviewed from jail -- estimating that "half the team probably smoked spice."
"It's hard to be more wrong than that. The facts and our drug testing results simply do not support such a claim," Jacobs said.
The ESPN report came out a day after another story harshly critical of Auburn and its football team was published on roopstigo.com. This story, written by former New York Times and Sports Illustrated reporter Selena Roberts, includes interviews with several ex-Tigers, though it focuses primarily on another of the four former Auburn players arrested in 2011, Mike McNeil. (McNeil was not interviewed in the ESPN piece).
Auburn athletic officials, former coach Gene Chizik, Auburn police and other officials declined to comment, the roopstigo.com story states. CNN also sought but did not get comments from these key figures beyond the Auburn athletic statements.
The roopstigo.com report includes several allegations from ex-players.
McNeil, for example, said one of his grades mysteriously changed from failing to passing, days after his professor told him otherwise. He also alleged that up to $500 -- far more than the $50 per day allowed by the NCAA -- was spent to entertain and take care of one prized football recruit during his visit to campus.
Receiver Darvin Adams also alleges in the story that he was offered unspecified financial incentives to stay at Auburn, for his senior year and not enter the NFL Draft pool. And McNeil said he was given $400 after practice one day in 2007 by then-assistant coach Will Muschamp, now head coach at the University of Florida.
University of Florida spokespersons did not immediately respond to a CNN request Friday night for comment. But Muschamp did reject this claim in comments to The Gainesville Sun.
"Totally deny it. I don't know where this is coming from," Muschamp said.
And Chizik, who was dismissed as Auburn's coach last fall, denied payments were made to players or grades were changed, among other allegations in the roopstigo.com report.
"Ms. Roberts' story is long on accusation and inference, but short on facts and logic," Chizik said in a statement, posted on al.com.
"It is noteworthy that the story comes just days before a player mentioned most prominently in the article is set to go to trial for felony armed robbery," he added, referring to McNeil. "The statements are very generalized accusations devoid of substance."