Walgreens shares tumbled early Thursday after the drugstore chain signaled that more store closings are on the way, missed earnings expectations for its third quarter and cut its annual forecast.

The company said it was finishing a multiyear plan to shutter some underperforming U.S. stores, but it didn’t detail how many were targeted.

Walgreens and major competitors like CVS and Rite Aid — which is going through a bankruptcy reorganization — have already closed hundreds of stores over the past few years. The companies have dealt with challenges that include years of tight reimbursement for their prescriptions and rising costs for running their locations.

Plus, analysts say they’ve also been hit by growing competition from Walmart, Amazon and other discount reta…