Activist investor Jana has yet to speak with Whole Foods management

Whole Foods jumps on Jana stake

Activist investor Jana Partners is attempting to engage with Whole Foods Market CEO John Mackey, sources told CNBC, but the firm has yet to speak about its ideas for the grocer with the company's management.

Earlier Monday, shares of Whole Foods jumped nearly 10 percent after Jana took a nearly 9 percent stake in the company and suggested it should consider putting itself up for sale.

In a regulatory filing Monday, Jana said it is looking to first address Whole Foods' "chronic underperformance" and secondly to make changes in the board and senior management. Also, it plans to looks for ways to improve real estate and capital allocation strategies for Whole Foods as well as discuss the small-store format.

Jana, now the second-largest shareholder of the grocery chain, wants to speed up a turnaround for the company and consider a possible sale.

The firm added that it believes Whole Foods "shares are undervalued and represent an attractive investment opportunity." The investor group also said it has "substantial experience" in the grocery and food sectors and intends to have discussions with the current board and management about making changes.

"Whole Foods Market welcomes investment in the company and is open to the views and opinions of all of our shareholders," Whole Foods spokeswoman Brooke Buchanan responded, in a statement late Monday. "We value constructive dialogue toward our shared goals of creating shareholder value, successfully executing on our strategic priorities and taking actions that will position the company for continued success."

Whole Foods, a Texas-based chain, has been struggling as other grocers make inroads into its natural and organics foods business. The company also has faced deceleration in customer counts and average purchase amounts. Both trends — combined with overall food price deflation — have contributed to Whole Foods slashing forecasts and posting same-store sales declines for the past six straight quarters.

Whole Foods had been attempting to trim its costs by closing nine stores and abandoning a goal to open 1,200-plus stores.

Jana Partners declined comment beyond its regulatory filing.

—Reporting by CNBC's Scott Wapner. Written by Mike Calia and Jeff Daniels.