WASHINGTON (CNN) -- Contractors on the problem-plagued website for President Barack Obama's signature health care reforms blamed the government and each other, but not themselves, at the first Congressional hearing on the troubled online enrollment system.
Angry exchanges between Republicans who oppose Obamacare and Democrats defending it erupted repeatedly, while officials of companies hired to create the HealthCare.gov website insisted their work went fine even though the software buckled when the system went online on October 1.
Complaints about logging in, lengthy delays, incorrect information relayed to insurance companies and other problems fueled continued GOP attacks on the 2010 Affordable Care Act that was upheld by the Supreme Court last year.
Rep. Fred Upton of Michigan, the chairman of the House Energy and Commerce Committee, called the rollout of the website "nothing short of a disaster," noting that contractors at the hearing previously "looked us in the eye and assured us repeatedly that everything was on track, except that it wasn't."
Democrats, however, accused Republicans of continuing a campaign to sabotage the health care reforms instead of working to fix problems in the system intended to help millions of uninsured Americans obtain affordable health coverage.
They noted that media headlines in 2006 blared similar descriptions of rollout problems with the Medicare Part D prescription drug reforms of the Bush administration, but that Democrats then worked with Republicans to resolve the issues instead of trying to scrap the legislation.
"The Republicans don't have clean hands coming here. Their effort is not to make things better," said Democratic Rep. Frank Pallone of New Jersey. "Let the goal here be to fix it, not nix it."
In the first detailed account of what happened, officials of four contractors involved in the website creation described a convoluted system of multiple companies operating separately under the oversight of the federal Centers for Medicaid and Medicare Services, a part of the Department of Health and Human Services.
Each said their individual components generally performed as planned after internal testing, but all conceded that CMS failed to conduct sufficient "end-to-end" testing of the entire system before the launch.
Unexpected volume at the start overwhelmed the entry portal, noted Andrew Slavitt of Optum, the company that handled the "enterprise identity management" or EIDM tool blamed for the initial blockages.
Slavitt, however, blamed the government, saying that "it appears that one of the reasons for the high concurrent volume at the registration system was a late decision requiring consumers to register for an account before they could browse for insurance products."
"This may have driven higher simultaneous usage of the registration system that wouldn't have otherwise occurred if consumers could 'window shop' anonymously," Slavitt said.
Slavitt said the EIDM tool was fixed a week after the launch and now could process the high volumes with low to zero error rates.
Another contractor, Cheryl Campbell of CGI Federal, said there should have been more end-to-end testing but added that plenty of time remained to fix the problems.
"The system is working, people are enrolling, but people will be able to enroll at a faster pace" as troubles get resolved, Campbell said, adding that her company expects the online system to be able to enroll Americans seeking health insurance by January 1.
She rejected media reports that the system needs to be scrapped or that five million lines of code must be rewritten.
Campbell also said the software program was unprecedented, noting that it "for the first time in history" combines the process of enrolling and selecting health insurance with determining eligibility for government subsidies "all in one place."
In her prepared testimony, Campbell said that "unfortunately, in systems this complex with so many concurrent users, it is not unusual to discover problems that need to be addressed once the software goes into a live production environment."
"This is true regardless of the level of formal end-to-end performance testing -- no amount of testing within reasonable time limits can adequately replicate a live environment of this nature," she added.
To accentuate progress on the website, two Democratic panel members said during the hearing that either they or their offices were able to use the website to determine health insurance options available to them on Wednesday or Thursday.
The White House and Health and Human Services Secretary Kathleen Sebelius make the same argument, saying the initial problems in accessing the website have eased.
Sebelius has brought in tech experts from Silicon Valley and elsewhere to work with the contractors on eliminating problems, with acting Office of Management and Budget Director Jeff Zients overseeing the effort.
"The work of constantly improving the website will continue day by day," White House spokesman Jay Carney said Wednesday. "A week from now, it's going to be better than it is today."
The Energy and Commerce Committee isn't the only one probing Obamacare in light of its issues. So, too, is the House Ways and Means Committee and the House Oversight and Government Reform Committee.
The latter sent an eight-page letter Wednesday night to 11 contracting firms involved in putting together HealthCare.gov giving them two days to provide documents, meeting lists and all communications with the Obama administration on the project, committee spokeswoman Caitlin Carroll said.
The fact all three committees are in the same chamber -- which is led by Republicans -- is likely no coincidence. The GOP has and continues to staunchly oppose Obamacare, even trying unsuccessfully to make defunding or delaying it requirement before it would fund the government.
The White House has pushed back against Republicans and some Democrats who have urged an extension of the open enrollment period beyond March 31 and/or a delay in penalties for those who don't sign up for insurance on time because of the website issues.
The Obama administration is moving to clarify confusion on when people need to sign up for health care, and it has plans to issue new guidelines to this point soon.
Still, Health and Human Services spokeswoman Joanne Peters insisted "the individual mandate timing" -- i.e. the requirement for a person to have insurance by March -- "has not changed. ... It was true this morning. It is true tonight."
CNN's Lisa DeJardins and Adam Levine contributed to this report.