The National Republican Congressional Committee says it was hit with a "cyber intrusion" during the 2018 midterm campaign and the breach has been reported to the FBI.
Committee spokesman Ian Prior says Tuesday that the intrusion was by an "unknown entity," but an internal investigation also has been launched.
The statement did not provide additional details about the incident, but added the security of the committee's data is of paramount concern.
The FBI did not immediately respond to a request for comment.
In March, NRCC Chairman Steve Stivers said the committee has hired multiple cybersecurity staffers to work with its candidates and promised to do more.
Politico first reported the news.