Their move followed a two-hour private conference call and fresh signs that their support for Paterno was waning.
"There's been a lot of discussion between the trustees, and I think Coach Paterno's support has eroded," said a person who was briefed on the talks but asked not to be named. "I don't know if it's eroded enough to end his career. That remains to be seen."
Two trustees told The Inquirer that the board's scrutiny will also extend to other university leaders, particularly longtime president Graham B. Spanier.
"This slipped through the crack," said one trustee, who spoke on condition he not be identified. "And the trustees aren't going to let that happen again."
A grand jury report unsealed Saturday said Sandusky, 67, molested eight boys between the mid-1990s and 2008, at home, on campus, and on team trips. After retiring in 1999, Sandusky kept an office at the team's football complex and university privileges as an emeritus coach.
Two administrators, athletic director Tim Curley and senior vice president Gary Schultz, are accused of failing to report a 2002 sex assault by Sandusky and of lying about it to the grand jury investigating the complaint. All three men have denied any wrongdoing.
As mothers of two of the alleged victims spoke out Tuesday, Pennsylvania State Police said a potential ninth victim, a man in his 20s, had come forward to say Sandusky abused him a decade ago in Centre County.
Like the others, the new accuser, whom police did not identify, said he met Sandusky through the Second Mile, a charity for the underprivileged founded by the coach. Sandusky routinely brought boys from the Second Mile to Penn State practices and games, and helped run summer camps for them on campus.
Prosecutors have said that the investigation is ongoing but that Paterno is not a target. The grand jury presentment says that when a graduate assistant told him he had seen Sandusky rape a boy in the team showers in 2002, Paterno passed on the allegation to athletic director Curley, but did nothing else.
In a statement released Sunday, Paterno said the assistant had told him about "inappropriate conduct" but not a sex assault. Paterno said he believed he "did what I was supposed to do" in reporting the information to the athletic director because Sandusky was no longer an assistant coach.
On Tuesday, school officials abruptly canceled what was to be Paterno's first public appearance since the scandal broke - a football briefing to talk about this week's home finale against the University of Nebraska.
"Due to the ongoing legal circumstances, centered around the recent allegations and charges, we have determined that today's news conference will not be held and will not be rescheduled," spokesman Jeff Nelson told more than 100 journalists outside the Clemens Family Football Team Complex.
The 84-year-old Paterno told a crush of reporters and fans outside his house that he hoped to soon be able to say more about the case.
"I know you guys have a lot of questions and I was hoping I was going to be able to answer them today," he said before getting into a car waiting to take him to the team's midafternoon practice. "We'll try to do it as soon as we can."
His son Scott said school officials had canceled the news conference, not his father. Scott Paterno also challenged a New York Times report saying university administrators were preparing for Paterno to leave or be ousted in days or weeks.
"At this point in time there has been no discussion with the coach about retiring," Scott Paterno said in the driveway outside his father's house. "There have been no discussions with the coach about stepping down. And as far as he is concerned, he will be coaching the team on Saturday. He's looking forward to it."
The case has stirred national headlines and outrage from advocates and others who questioned how and why Sandusky's alleged crimes went undetected or unpunished for a decade.
Those calls continued Tuesday. U.S. Rep. Patrick Meehan, (R., Pa.) urged U.S. Education Secretary Arne Duncan to investigate whether federal laws were broken in the failure to report allegations of sexual abuse.
U.S. Sen. Bob Casey (D., Pa.) said "there's some accountability issues here - people who may not have broken the law but have a duty that they may not have discharged."
State Senate Majority Leader Dominic Pileggi (R., Delaware) went further, calling for Spanier to offer a full accounting of university officials' actions or to be prepared to resign.
The school's trustees learned about the complaints against Sandusky about a year ago, months after state police began investigating an allegation that he had abused a Clinton County boy. Since 1998, a number of grand juries had investigated similar allegations against Sandusky.
"The trustees were told that there were three or four grand juries looking into Sandusky's conduct and that none of them came back with a true bill," said the person close to the board.
The grand jury report said university police and state public welfare officials first investigated Sandusky in 1998 after the mother of a boy complained that the coach had grabbed her son in the shower.
Two years later, a janitor in the football complex told his supervisor he saw Sandusky perform oral sex on a boy in the facility showers, the grand jury report said. No one reported that allegation to law enforcement.
After the accusation against the coach in 2002, Spanier and former counsel Wendell Courtney were also informed of concerns about Sandusky's behavior, as were executives at his charity, the grand jury said.
Sandusky resigned from the organization last year as the investigation intensified.
He had been scheduled to appear at a preliminary hearing on the charges Wednesday, but a Centre County Court judge agreed to continue that proceeding until December.
On Sunday, university officials said Schultz was retiring and Curley would take a leave of absence until the case is resolved. Curley's and Schultz's attorneys say they will challenge the contention that their clients were required to report abuse under state law.
The trustees are scheduled to gather in State College for their regular meeting on Thursday and Friday. One report said they could reconvene for a private meeting as soon as Wednesday night.
The board said it would appoint a special committee at its meeting Friday "that will have whatever resources are necessary to thoroughly fulfill its charge, including independent counsel and investigative teams."
Its results will ultimately be presented at a public meeting, the trustees pledged.
"This Special Committee," the board said in a statement, "will be commissioned to determine what failures occurred, who is responsible and what measures are necessary to ensure that this never happens at our university again and that those responsible are held fully accountable."
When the scandal first broke, Spanier said Curley and Schultz had his "unconditional support," a pledge that stirred backlash from mothers of two of the alleged victims.
"My son is extremely distraught, and now to see how we were betrayed, words cannot tell you," one of the women told the Harrisburg Patriot-News. "To see that Graham Spanier is putting his unconditional support behind Curley and Schultz when he should be putting his support behind the victims, it just makes them victims all over again."
Spanier and his wife, Sandra, a professor of English, were to be honored Wednesday at an annual school fund-raising dinner. The dinner has been canceled.
Contact staff writer John P. Martin at 215-854-4774, firstname.lastname@example.org or @JPMartinInky on Twitter.
Contributing to this article were Inquirer staff writers Jake Kaplan, Melissa Dribben, Michael Matza, Karen Heller, Jeremy Roebuck, Amy Worden, and Joseph Tanfani. It also contains information from the Associated Press.