Shares of Whole Foods Market ( WFMI) plunged after hours Wednesday, as the company posted a 15% increase in second-quarter earnings but warned of slower growth next year.

The Austin, Texas-based company said net income rose to $32.9 million, or 50 cents a share, up from $28.7 million, or 45 cents a share, in the same period last year.

Sales increased by 22% to $917.6 million from $749 million in the previous year, driven by a 9% weighted average year-over-year square-footage growth and comparable-store sales growth of 14.1%.

The company's earnings per share came in just under analysts' forecast of 51 cents a share and above the revenue consensus of $911 million.

For the full year, the company expects same-store sales to range between 11% and 13% and sees earnings per share at the higher end of its previously stated guidance of $2.03 to $2.10. The consensus estimate is $2.10 a share.

For 2005, the company said that although it anticipates earnings to grow between 15% to 20%, the company indicated that, "earnings-per-share growth could be lower than sales growth due to an expected acceleration in square-footage growth, which would result in higher pre-opening expenses and could have some negative impact on store contribution."

Shares of Whole Foods moved more than 6% lower in after-hours trading, after losing almost 2% to $86.01 in the regular session.