Problems keep mounting in the administration's attempt to sell health insurance online. A data center critical to the operation of Healthcare.gov, the federal insurance marketplace, experienced an outage over the weekend. The failure affected the Healthcare.gov data services hub, which coordinates eligibility checks, and therefore also impaired local exchanges in 14 states and Washington, DC.

The data center is run by Verizon's Terremark, which says the failure occurred during planned maintenance. Neither the administration nor Verizon has given an estimate for how long it will take to fix.

Healthcare.gov, the keystone of President Barack Obama's Affordable Care Act, has had a long list of technical problems since launching on October 1st. The administration has announced a full-court press-style effort to get the website working smoothly. The data center failure represents another setback preventing people from signing up — and more ammunition for the president's opponents, who want to repeal the law.

Department of Health and Human Services chief Kathleen Sebelius will testify before Congress on Wednesday, where she is expected to answer questions about the website's bumpy rollout.

Update, 2PM: The White House has announced that Verizon has fixed the problem and the Healthcare.gov marketplace is working again.