From the FDA:

Clif Bar & Company is initiating a voluntary recall of CLIF BAR® Nuts & Seeds energy bars, CLIF BAR® Sierra Trail Mix energy bars, and CLIF® Mojo® Mountain Mix® trail mix bars, sold nationally, after its ingredient supplier, SunOpta, was found to have distributed sunflower kernels that may be contaminated with Listeria monocytogenes (L.mono).

Only the flavors meeting the following criteria are affected by the recall:

CLIF BAR® Nuts & Seeds energy bar all pack configurations with “best by” date ranges starting 08JUN16 through 21JAN17
CLIF BAR® Sierra Trail Mix energy bar all pack configurations with “best by” date ranges starting 05JUN16 through 24MAR17
CLIF® Mojo® Mountain Mix® trail mix bar all pack configurations with “best by” date ranges starting 16JUN16 through 02FEB17

You can read the entire press release HERE.