The Penn State board of trustees said today they ignored early warnings of a child abuse sex scandal because they were told three previous grand juries had investigated and failed to charge former assistant coach Jerry Sandusky with a crime.

But the Pennsylvania attorney general's office said that the board's explanation is wrong because there were no prior grand jury investigations into Sandusky, said Nils Hagen-Frederiksen, spokesman for the office.

"It's not true," Nils Hagen-Frederiksen, spokesman for the office, told ABC News today.

Members of the board have repeatedly made the claim about previous grand juries in recent days and repeated the claim during a press conference following a board meeting today. 

The board has come under fire for not being better prepared to handle the charges of child sexual abuse against Sandusky when local newspapers had written about the grand jury investigation as early as spring, 2011. Board members say they were briefed on the investigation, but paid little attention to it because their attorney, Cynthia Baldwin, explained that Sandusky had been investigated by three grand juries previously with no results.

The board has also been criticized for firing football coach Joe Paterno and school president Graham Spanier for not reacting firmly enough when told of  Sandusky's alleged behavior.

Sandusky had been investigated by police for alleged inappropriate behavior with a boy in 1998, but the probe concluded with no charges.

There had not been previous grand jury investigations into Sandusky before the one that indicted him in November.

Board spokesman Lanny Davis said the board members were "confused," and blamed Spanier for not alerting them.

"They can't remember. They're confused, they thought it was three or four investigations, but can't remember whether they were told three or four investigations or grand jury investigations," he said.

"The most important thing is that Spanier didn't make it a big deal. Why didn't he tell them more in May? Why didn't he say anything about testifying?" Davis asked.

Cynthia Baldwin, who was previously a Pennsylvania Supreme Court Justice, was unable to be reached for comment, and has not confirmed or denied the board's claims.