Four staffers for ex-Rep. Aaron Schock, R-Ill., have been issued grand jury subpoenas as part of an investigation into their former boss’s improper spending.

As the House convened after a two-week recess Tuesday, the clerk read each staffer’s letter to Speaker John A. Boehner, R-Ohio, notifying him they had been served with a grand jury subpoena for testimony by United States District Court for the Central District of Illinois.

House rules stipulate that an employee of the House must notify the speaker if he or she receives a subpoena.