Washington (CNN)The FBI and the federal prosecutors in Illinois are investigating whether Rep. Aaron Schock broke the law in accounting for campaign expenses, according to people familiar with the matter.
The FBI is delivering subpoenas in Washington and Illinois, according to two people familiar with the investigation.
Investigators from the U.S. Postal Inspection Service and IRS are pursuing various parts of the Schock investigation, according to law enforcement sources.
A U.S. law enforcement official says the investigation is at an early stage. Justice Department officials were monitoring published reports about Schock's expense troubles and were taken by surprise when he announced his resignation, according to another U.S. law enforcement official.
CLARIFICATION: This story has been updated to clarify the ownership of a personal car for which Rep. Aaron Schock allegedly sought improper reimbursement.