Amazon.com Inc. employees in Bessemer, Ala., will vote by mail next month in a rerun election on whether to unionize, the National Labor Relations Board announced Jan. 11.

Accusing Amazon .com Inc. of misconduct, the retail union that lost a hotly contested election at the company’s Alabama warehouse has asked federal officials to set aside the results.

Amazon.com Inc. warehouse workers in Minnesota plan to strike during the online retailer’s summer sales extravaganza, a sign that labor unrest persists even after the company committed to paying all employees at least $15 an hour last year.