HealthCare.gov offline for nearly six hours on deadline morning

The HealthCare.gov website is down for maintenance Monday, the final day of Affordable Care Act enrollment.

The site, which had been performing well under large volume as the sign-up deadline approached, has been unavailable since shortly after 3 a.m. Eastern Time.

Health and Human Services officials said it was a software bug that was being repaired. The site goes through routine maintenance at night, but this incident spilled into high-profile hours in the final day for most people to enroll in Obamacare.

'The tech team is working now to bring the system online as soon as possible. Consumers are able to leave their email and will be invited back when the system is available,' a spokesman said.

While March 31 is the official deadline, HHS has said people who tried to sign up on time and had problems can have additional time.

The call center is working. So is the 'window-shopping' function where people can peruse plans but not choose one.

Traffic has been extremely heavy for several days. HHS reported more than 2 million website visitors over the weekend.

A queuing mechanism is in place - a 'virtual waiting room' where people can leave an email and be notified when the site is less busy - but it has seldom been needed. The maintenance message that appeared this morning allowed people to send in their email for a notification when the system was available.