DC Health Link is the health insurance marketplace for Washington, DC.
"I have been informed by the United States Capitol Police and DC Health Link of a data breach impacting members and staff. DC Health Link suffered a significant data breach yesterday potentially exposing the Personal Identifiable Information (PI) of thousands of enrollees," the letter said on Wednesday.
The size and scope of the breach is not known at present, but the FBI has informed the House that account information and personal identifiable information of hundreds of lawmakers and staff has been stolen, the letter said.
The personal data of any House member or an employee who used DC Health Link could have been compromised as a result of the breach, the letter also said.
At present, there is not a final list of all impacted persons, but one may be finalized later in the day, the letter added.
So far, it looks like House members were the main target of the attack, according to the letter.