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House Republicans are investigating the Obama administration's move to delay a key part of the health care overhaul, claiming the announcement was "completely at odds" with prior claims that ObamaCare was running on schedule and questioning what provisions might be delayed next.

"It's clear we have no idea the full scope of delays and disarray that may be coming. The American public deserves answers," Rep. Fred Upton, R-Mich., chairman of the House Energy and Commerce Committee, said in a  statement.

Republicans on Upton's committee fired off a pair of letters on Wednesday to both the Treasury Department and Department of Health and Human Services. They demanded records detailing deliberations regarding the recently announced delay and ongoing talks about other "elements" of the law that some groups want "changed, delayed or repealed."

The intense scrutiny comes after the administration, at the start of the holiday week, announced it was delaying until 2015 a requirement that large employers provide health insurance or pay a fine. In explaining the decision, officials said they were responding to businesses' concerns that the reporting requirements were too onerous -- they said they would simplify that system and give employers an additional year to comply.

Senate Democratic Leader Harry Reid described the change as merely a "willingness to be flexible" and work with businesses.

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    "Flexibility is a good thing," he said. "It is better to do this right than fast."

    But Republicans, while claiming the decision was a political move to push the mandate past the 2014 elections, said the abrupt delay was also a sign of the broader problems with the law.

    Many of the law's most significant provisions are still scheduled to take effect at the beginning of 2014, and Republicans want to know whether there are other under-the-radar problems that the administration has not yet acknowledged.

    Upton and the other Republicans who wrote to the administration said they had been hearing complaints for years about the employer mandate's requirements. But they noted the administration did not admit the problems until this week.

    "The acknowledgement that a delay in the law's implementation is needed is completely at odds with previous public statements made by administration officials," they wrote.

    It's ultimately unclear whether other major provisions could be delayed. The employer mandate, while significant, will affect a limited number of businesses -- those with 50 or more full-time employees who weren't already providing health coverage. But the so-called "individual mandate" -- the requirement on individuals to buy insurance and the provision that was at the heart of last year's Supreme Court challenge -- supposedly is still on schedule.

    In their letter, House Republicans specifically inquired about the status of that mandate, as well as the expansion of Medicaid, the newly created insurance exchanges and other fees associated with the law.