Fewer than 50,000 people had successfully navigated the troubled federal health-care website and enrolled in private insurance plans as of last week, two people familiar with the matter said, citing internal government data.

The figure is a fraction of the Obama administration's target of 500,000 enrollees for October. The early tally for the HealthCare.gov site, which launched Oct. 1, worries health insurers that are counting on higher enrollment to make their plans profitable.

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