A former NCAA official said Monday that Texas A&M quarterback Johnny Manziel should not be eligible to play until the investigation over whether he accepted money for signing autographs is completed.

That review might grow in scope after ESPN reported Monday that the Heisman Trophy winner appeared at even more signing events than had been first reported. Manziel is estimated to have signed his name more than 4,400 times in less than a month at a total of six signing sessions.

"Outside The Lines" previously reported that Manziel accepted thousands of dollars for signing memorabilia earlier this year and that he had agreed to a "five-figure flat fee" with Drew Tieman, an autograph broker, for signing memorabilia at the site of the 2013 BCS Championship Game. Witnesses say they saw Manziel autograph products in January but did not see money exchange hands.

The NCAA is investigating the allegations, and thus far, Manziel has not commented. Manziel's attorney, Jim Darnell, recently told USA Today that his client is cooperating with the NCAA.

"I can't say much other than we're working through the process," Darnell said. "We think when all this comes out on the other end, he'll be the starting quarterback for the Aggies against Rice."

The Aggies open the season Aug. 31 against the Owls.

Former NCAA enforcement director Mark Jones told the San Antonio Express-News that Manziel should be benched while the NCAA continues its probe.

"No one wants to play an athlete who's later determined to be ineligible, especially such a high-profile player," Jones said. "You don't want to risk having to vacate those games later on."

Florida attorney Michael Buckner, who focuses on NCAA investigations, agreed.

"A&M will not play Johnny Manziel if there's any question that he could be ineligible," Buckner told the Express-News.

He did not want to guess when the investigation might be finished. Texas A&M also is conducting its own investigation.

"But I would think it is going to be done in an expeditious manner," Buckner said. "I'm pretty sure all sides are working feverishly at this because there is a lot at stake."

As a student-athlete, Manziel must cooperate with the NCAA investigation. If he doesn't, he could be subject to being declared ineligible.

"He is required to tell the truth," Buckner said.