A senior administration official involved in implementation of President Barack Obama's health care plan says the program's sign-up website has improved since its launch more than a month ago and is still improving.

Centers for Medicare and Medicaid Services Administrator Marilyn Tavenner testifies before the House Ways and Means Committee (Chip Somodevilla/Getty Images)

Marilyn Tavenner told a Senate committee that the site is now able to process nearly 17,000 registrants per hours with almost no errors.

In her opening remarks at a congressional hearing Tuesday, Tavenner did not say how many individuals have enrolled for health care through the site. The administration has steadfastly refused to divulge those numbers, and says they will be made available at mid-month.

Tavenner is head of the Centers for Medicare and Medicaid Services.