The U.S. health secretary, Sylvia Mathews Burwell, said her agency made a mistake when it added dental-plan customers to recent figures on Obamacare enrollment. Republicans said she owes them an explanation.

The disclosure by Burwell’s department that it accidentally added 380,000 people in dental plans to enrollment figures under the Patient Protection and Affordable Care Act provided a new opening for critics. Representative Darrell Issa, a California Republican and chairman of the House committee that revealed the commingling of dental and health enrollment, said Burwell needs to clarify how the error happened.

Her agency “must provide a clear and detailed account of who knew about this decision and when they knew it,” Issa said.

Adding dental plans to health-plan enrollment brought the total to 7.3 million as of Aug. 15 and 7.1 million two months later, Kevin Griffis, a spokesman for Burwell’s department, said in an e-mail. The two figures had previously been reported separately.

Without dental, enrollment would have been just less than 7 million in August and was about 6.7 million in October, Griffis said. The inclusion of the dental plans helped the total enrollment figure surpass the threshold of 7 million -- the original projection for 2014 by the Congressional Budget Office. That number had been adopted by the government as a goal before sign-ups began in October 2013.

‘Quickly Corrected’

In social-media messages today, Burwell didn’t provide details on how the error happened.

“While we understand some will be skeptical, our clarity that this is mistake and the fact that we have quickly corrected the numbers should give people confidence,” Burwell told MSNBC host Chris Hayes in a Facebook chat.

Later in the same chat, echoing a post on her Twitter account, she called the mistake “unacceptable” and said she is “communicating this clearly throughout the department.”

“We will be putting in place measures to ensure that this kind of mistake does not occur again after we understand why it happened,” she told Hayes.