Pennsylvania’s beleaguered pension fund for educators has hired yet another outside law firm — this time to consider suing the consulting firm that admitted botching a key profits calculation in an error that has triggered an ongoing FBI investigation.

The board of the $75 billion pension plan has hired the big Philadelphia firm of Blank Rome to pursue “potential litigation” following the admission from consultant Aon that its “inadvertent clerical mistakes” led the fund to adopt a false and exaggerated figure for profits.

The plan — the Public School Employees’ Retirement System — later had to correct that number, forcing 100,000 school employees to pay more into the pension plan. Under the state “risk share” law, how much teachers pay into the fund depends partly on its investment profits.

PSERS had agreed to pay the Chicago-based Aon $7.2 million for investment advice and performance measurements in contracts dating back almost a decade —– and the fund continues to employ the firm. But Aon’s contract also includes a promise to repay “all claims” that may result from failure to comply with its terms.

Aon had no comment. Early last year, the firm said “human error” and mistakes in data entry had caused “data corruption.” “Aon sincerely regrets the error,” the firm wrote the pension plan.

PSERS would not elaborate on hiring Blank Rome. People familiar with the decision said the law firm will review options forlegal action, including a possible lawsuit against Aon.

After the retirement system made the mistake public last spring, the U.S. Attorney’s office in Philadelphia sent FBI agents with subpoenas to learn more about what went wrong. The Securities and Exchange Commission is also investigating the miscalculation, as well as possible gifts by Wall Street advisers to PSERS employees, and whether that influenced pension contracts.

The embarrassing error fueled dissent and tensions on the board. The fund’s two top executives announced their retirement last fall. No one has been charged with wrongdoing.

Even before Monday’s board vote to hire Blank Rome, the pension system had paid out $4.5 million to at least seven other law firms and a financial consultant brought on to deal with the faulty calculation and the federal probes. The biggest single payment — $1.9 million so far — has gone to the Philadelphia firm of Morgan, Lewis & Bockius to deal directly with the federal investigators.

Because of the law linking profits to payments by teachers and other school employees, the profit figure was a source of great anxiety for the fund. The original calculation had wrongly pumped up PSERS revenues by $150 million — just enough, it seemed, for the fund to avoid increasing payments from working educators. Then, when the figure was corrected, levies rose for educators.

Another outside law firm, Womble Bond Dickinson, was hired to conduct an investigation parallel to the FBI probe.

The input error aside, the Womble report revealed that the board adopted the mistaken number during the key 2020 meeting at which the previous PSERS management chose not to answer questions from skeptical board members about performance figures. The Womble lawyers also suggested that the board was rushed by managers into approving what was later revealed to be an inaccurate number.

In his response filed with the Womble report, former PSERS executive director Glen Grell revealed that he had unsuccessfully urged the board to fire Aon after the scandal broke in March 2021 because of the mistake. He drafted a news release — never issued, but reprinted in the Womble document — ripping into Aon, saying, “our trust is now broken because Aon allowed this error to go unnoticed for so long.”

The Womble report doesn’t make clear why Aon was kept on despite Grell’s urging that it be fired. The report says Aon answered written questions but would not sit down for an interview.

Grell announced his retirement late year, along with James Grossman Jr., the fund’s chief investment officer.

In dealing with another lingering issue, PSERS on Monday also hired a Philadelphia company, Rittenhouse Appraisers, to value about 15 real estate parcels that the fund executives acquired for the agency in downtown Harrisburg between 2017 to 2019 for a secret urban renewal plan.

The Inquirer later learned of a PSERS proposal to partner with Harrisburg University of Science and Technology on an office tower, but nothing ever came of that. PSERS has demolished buildings on the lots, which remain empty. The results of these appraisals will be made public, the board said in a resolution approving Rittenhouse’s hiring.

In total, the fund spent about $10 million to buy, demolish and maintain a mix of industrial buildings and parking lots near its offices. Womble, in its report, pointed out that many of the buildings were purchased without the staff first obtaining appraisals.

Rittenhouse has appraised a wide range of commercial real estate. Its clients have included the U.S. Army Corps of Engineers and the federal General Services Administration, owner Carlo Batts said.