HARRISBURG — Pennsylvania’s largest public pension system disclosed late Tuesday night that it is dealing with a federal investigation, although officials atop the $64 billion Public School Employees’ Retirement System have yet to publicly disclose the nature or scope of the inquiry.

The disclosure comes less than two weeks after the system said it is investigating a consultant’s calculation about the fund’s investment performance that is apparently wrong.

The board approved a one-sentence resolution to hire a law firm to represent it “in matters relating to a federal investigation” and any related issues.

The resolution was posted to PSERS’ website. The law firm has not been named.

Board members — including state lawmakers, two members of Gov. Tom Wolf’s Cabinet and state Treasurer Stacy Garrity — have not spoken publicly about it.

The calculation — 6.38% growth over the nine years ending last June 30 — was slightly above a 6.36% growth threshold, thus protecting nearly 100,000 active school employees who are retirement system members from seeing a higher risk-sharing contribution rate kick next July 1.