The F.D.A. said Granny Smith apples may be linked to the Listeria outbreak that killed six and sickened 32 people.

WASHINGTON — Bidart Brothers Apple Packing, Shafter, Calif., is recalling any Granny Smith apples the company sold to food processors in 2014 that may have been used in the making of caramel-coated apples. The Food and Drug Administration said the apples may be linked to the Listeria outbreak associated with caramel apples, but added that the agency also is investigating common sources of caramel, caramel ingredients, sticks or packaging as the possible source.

Three makers of caramel apples, the Happy Apple Co., Washington, Mo.; California Snack Foods, El Monte, Calif.; and Merb’s Candies, St. Louis, have launched recalls due to the outbreak and all three received some apples from Bidart Brothers, according to the F.D.A.

On Dec. 31, the Centers for Disease Control and Prevention said 6 people had died and 32 had become ill due to Listeria. The outbreak has been identified in 11 states, including Arizona (4 illnesses), California (2), Minnesota (4), Missouri (5), Nevada (1), New Mexico (6), North Carolina (1), Texas (4), Utah (1), Washington (1) and Wisconsin (3).

During the outbreak the F.D.A. has maintained its recommendation that consumers avoid eating commercially-produced, pre-packaged caramel apples.