The Justice Department is investigating Democratic Rep. Cori Bush of Missouri for misuse of funds, a senior congressional source with knowledge and a source familiar with the probe told CNN, after the DOJ subpoenaed the House Sergeant at Arms Monday for documents related to the matter.

Separately, two law enforcement sources told CNN the investigation is targeting Bush, who is the subject of a corruption probe.

According to the source familiar with the probe, the subpoena involves the misuse of funds surrounding security.

Bush confirmed in a statement that the Justice Department is reviewing her campaign’s spending on security services and says she is fully cooperating with the investigation.

“First and foremost, I hold myself, my campaign, and my position to the highest levels of integrity,” Bush said in the statement. “I also believe in transparency which is why I can confirm that the Department of Justice is reviewing my campaign’s spending on security services. We are fully cooperating in this investigation, and I would like to take this opportunity to outline the facts and the truth.”

Bush maintained she has not used any federal tax dollars for personal security services and that she complied with House rules. Bush further explained she retained her husband’s security services “because he has had extensive experience in this area, and is able to provide the necessary services at or below a fair market rate.“

The Justice Department declined to comment.

The House clerk on Monday read a letter on the floor from the Sergeant at Arms informing the chamber of the subpoena.

“The office of the Sergeant at Arms for the House of Representatives has been served with a grand jury subpoena for documents issued by the US Department of Justice,” the clerk said, reading from the letter.

“After consulting with the Office of General Counsel, I have determined that compliance with a subpoena is consistent with the rights and privileges of the House,” they continued.