HARRISBURG, Pa. -- Former Penn State President Graham Spanier was charged Thursday with hushing up child sex abuse complaints against Jerry Sandusky, taking the allegations of a "conspiracy of silence" to the highest level of the university and marking another chapter in the dramatic downfall of a once-renowned administrator.

Former Penn State president Graham Spanier became the third school official to be charged with crimes in the alleged cover-up in the Jerry Sandusky child sex abuse case. AP Photo/Carolyn Kaster

Prosecutors also added counts against two of Spanier's former underlings, Tim Curley and Gary Schultz, who were already charged with lying to the grand jury that investigated the former Penn State assistant football coach.

"This was not a mistake by these men. This was not an oversight. It was not misjudgment on their part," said state Attorney General Linda Kelly. "This was a conspiracy of silence by top officials to actively conceal the truth."

Spanier's lawyers issued a statement that asserted his innocence and described the new charges as an attempt by Gov. Tom Corbett to divert attention from the three-year investigation that began under his watch as attorney general.

"These charges are the work of a vindictive and politically motivated governor working through an unelected attorney general ... whom he appointed to do his bidding," the four defense lawyers wrote.

Corbett spokesman Kevin Harley said the defense statement "sounds like the ranting of a desperate man who just got indicted."

Curley and Schultz have repeatedly asserted they are innocent. A spokeswoman for their lawyers said they planned to respond later to the new charges.

At a Capitol news conference, Kelly said all three men "knowingly testified falsely and failed to provide important information and evidence."

Spanier was charged with perjury, obstruction, endangering the welfare of children, failure to properly report suspected abuse and conspiracy. Curley and Schultz face new charges of endangering the welfare of children, obstruction and conspiracy.

The charges were filed with a suburban Harrisburg district judge, whose office said Curley and Schultz were expected to be arraigned Friday afternoon and Spanier tentatively scheduled to appear Wednesday.

Sandusky, who spent decades on the Penn State staff and was defensive coordinator during two national championship seasons, was convicted in June of sexually abusing 10 boys over 15 years. He has maintained he is innocent and was transferred to a maximum security prison on Wednesday, where he is serving a 30- to 60-year sentence.

Curley, 58, the athletic director on leave while he serves out the last year of his contract, and Schultz, 63, who has retired as vice president for business and finance, were charged a year ago with lying to the grand jury and with failing to properly report suspect child abuse. Their trial is set for early January in Harrisburg.

Spanier, 64, of State College, had been university president for 16 years when he was forced out after Sandusky's November 2011 arrest. He remains a faculty member but was placed on paid leave Thursday.

Prosecutors said Spanier, Curley and Schultz knew of complaints involving Sandusky showering with boys in 1998 and 2001.

"They essentially turned a blind eye to the serial predatory acts committed by Jerry Sandusky," Kelly said.

The grand jury report included with the charges said "the actual harm realized by this wanton failure is staggering," and listed instances of abuse detailed at Sandusky's criminal trial that happened after 1998.

"The continued cover-up of this incident and the ongoing failure to report placed every minor child who would come into contact with Sandusky in the future in grave jeopardy of being abused," jurors wrote.