WASHINGTON — The federal health care website stumbled today on deadline day for new sign-ups.

Visitors to HealthCare.gov this morning saw messages that the site was down for maintenance. At times the visitors were also directed to a virtual waiting room — a feature designed to ease the strain on the site during periods of heavy use.

Administration spokesman Aaron Albright said the website undergoes “regular nightly maintenance” during off-peak hours and that period was extended because of a “technical problem.” He did not say what the problem was, but a statement from the Department of Health and Human Services called it “a software bug” unrelated to application volume.

Albright said consumers seeking to sign up will be able to leave their email and “will be invited back when the system is available.”

Consumers can also call 1-800-318-2596 to complete the application process.

Officials said the website wasn’t hacked. The site, which was receiving 1.5 million visitors a day last week, received about 2 million a day over the weekend.

Albright said the website is typically down for maintenance from 1 a.m. to 5 a.m. EDT, and that as a result of the technical problems the site was down for at least three additional hours this morning.