The on-line medical health insurance market for members of Congress and Washington, D.C., residents was subjected to a hack that compromised the non-public figuring out info of doubtless hundreds of lawmakers, their spouses, dependents and staff, in accordance with a letter from House leaders informing their colleagues concerning the breach and a memo from the Senate’s prime safety official.

The Capitol Police and the Federal Bureau of Investigation knowledgeable Speaker Kevin McCarthy, Republican of California, and Representative Hakeem Jeffries, Democrat of New York and the minority chief, of the assault on the D.C. Health Link market. Federal investigators had been in a position to buy private details about members of Congress and their households on the “dark web” due to the breach, the letter mentioned.

“Right now, our top priority is protecting the safety and security of anyone in the Capitol Hill community affected by the cyber hack,” Mr. McCarthy and Mr. Jeffries wrote on Wednesday, calling the incident an “egregious security breach.”

“The Office of the Chief Administrative Officer will be in contact with important resources including credit and identity theft monitoring services, which we strongly encourage you to utilize,” the lawmakers wrote.

The information of senators and their staffs had been additionally compromised, in accordance with an inside memo from the Senate sergeant-at-arms. That memo acknowledged that the compromised information included “full names, date of enrollment, relationship (self, spouse, child), and email address, but no other personally identifiable information.”

The trigger, measurement and scope of the info breach affecting D.C. Health Link was not instantly identified, in accordance with the House leaders, who wrote that they had been “being consistently briefed” concerning the matter by the police and the F.B.I.

But the net medical health insurance market serves about 11,000 members of Congress and their staffs, and practically 100,000 individuals total.

“This breach significantly increases the risk that members, staff, and their families will experience identity theft, financial crimes, and physical threats — already an ongoing concern,” Mr. McCarthy and Mr. Jeffires wrote. “Fortunately, the individuals selling the information appear unaware of the high-level sensitivity of the confidential information in their possession, and its relation to members of Congress. This will certainly change as media reports more widely publicize the breach.”

House leaders at the moment are demanding solutions from Mila Kofman, the director of the D.C. Health Benefit Exchange Authority, a private-public partnership liable for the District of Columbia’s on-line medical health insurance market. Mr. McCarthy and Mr. Jeffries despatched a sequence of pointed inquiries to Ms. Kofman on Wednesday.

Among them had been why the insurance coverage market had not formally alerted people whose information was compromised; what particular enrollee info was stolen; and what number of lawmakers had been impacted.

In an announcement on Wednesday night, Adam Hudson, a spokesman for the authority, confirmed the breach, saying that “data for some D.C. Health Link customers has been exposed on a public forum.”

Mr. Hudson mentioned the company had begun an investigation.

“Concurrently, we are taking action to ensure the security and privacy of our users’ personal information,” Mr. Hudson mentioned. “We are in the process of notifying impacted customers and will provide identity and credit monitoring services.”