WASHINGTON — The top watchdogs in the House demanded to know Tuesday why a personal laptop taken from a federal building in Washington state was used to conduct child-support audits, especially because it and other stolen hard drives may have contained millions of names and Social Security numbers.

The letter by the House government oversight panel’s Republican chairman and senior Democrat to Health and Human Services Secretary Sylvia Burwell comes about a week after GOP investigators began looking into the breach in Olympia, Wash., which authorities say affected as many as 5 million people.

“Your staff acknowledged that the use of personal equipment is a clear violation of HHS privacy and security policy,” Utah Republican Jason Chaffetz and Maryland Democrat Elijah Cummings wrote in the letter. The break-ins occurred in early February at the federal Office of Child Support Enforcement.

Chaffetz’s committee has been critical of data breaches under the Obama administration, including when the U.S. Office of Personnel Management said last year hackers committed an unprecedented theft of private data for millions of federal workers.

The letter comes a day after Chaffetz’s counterpart in the Senate, Republican Sen. Ron Johnson of Wisconsin, sent a similar message to Burwell asking what specific information was on the hard drives and when officials first became aware of the burglaries.

But Chaffetz and Cummings also questioned why HHS officials waited nearly two months to provide Congress with notification under the Federal Information Security Management Act, which they said requires notice no later than a week after a major incident took place. They also asked what databases could have been accessed.