Shares of Whole Foods fell by up to 10% in trading on Thursday, after the company reported second-quarter earnings.

On Wednesday, the company reported sales of $3.6 billion, a 10% increase but below investors' expectations for $3.7 billion, according to Bloomberg.

The company posted diluted earnings per share of $0.44, higher than the expectation for $0.42.

“Our results reflect another quarter of record sales and healthy returns on invested capital,” said CEO John Mackey in the statement.

“Our Whole Foods Market brand has helped lead the shift in consciousness toward fresh, healthy foods by offering the highest quality, broadest selection, and best customer service, and we believe we can triple the number of Whole Foods Market stores in the United States," he said.

Comparable store sales on a constant currency basis rose 3.6%.

The company also announced the launch of a new store concept “unlike anything that currently exists in the marketplace.”

The company said it is building a team solely to develop these stores and negotiate leases. It plans to open them next year, it said.

“We look forward to sharing more details about this exciting new venture sometime before Labor Day.”

For the full year, Whole Foods is forecasting sales growth of more than 9%, and comparable store sales growth “in the low to middle single digits.”

Organic food sales have exploded in the US, and that's not helping Whole Foods.

"We remain concerned about WFM's ability to revive sustained strong sales growth as competition intensifies," wrote S&P Capital IQ's Joseph Agnese in an email.

The firm lowered its 12-month price target to $13. It had previously been $60.