A copy of the letter, sent to an undisclosed list of recipients, was obtained by The Times.

The letter also said that the recipients must preserve any documents or information related to “the foundation’s mission and purpose for which funds are to be disbursed,” and to Ms. Coico, her immediate family members, or any entity with which Ms. Coico’s family had a financial relationship. The letter also ordered the preservation of any materials related to the Research Foundation, as well as “the purpose, receipt or use of contributions, grants, donations or other funding the foundation received.”

Among those who were asked to preserve documents were Ms. Coico; Maurizio Trevisan, the provost; and several senior officials in finance and development, according to three people who have been briefed on the matter, but asked to remain anonymous because of the federal investigation.

It is not exactly clear what, specifically, federal prosecutors are seeking at this point; a spokeswoman for Robert L. Capers, the United States attorney, declined to comment, citing office policy.

Ms. Kakar, a partner with Pryor Cashman L.L.P., did not respond to an email seeking additional details.

In a statement, City College said: “The 21st Century Foundation, a not-for-profit corporation that raises funds in support of the college, received a subpoena for some documents from the U.S. attorney’s office in Brooklyn. The foundation, assisted by its legal counsel, is responding to the subpoena. The administration of the college immediately directed all employees who interface with the foundation to cooperate fully in this process.”