Officials with First Interstate BancSystem Inc. plan to close eight Mountain West Bank branches in Montana when the companies complete their merger in October.

First Interstate announced it will close all three Mountain West branches in Missoula, one of two in Great Falls along with branches in Bozeman, Whitefish and Kalispell.

FIB plans to relocate Mountain West's main branch in Helena to its nearby retail banking center and drive-up facility and close its branch in downtown Helena.

In regulatory language, the closures of the downtown Helena branch as well as those in Great Falls, Bozeman, Kalispell and Whitefish are consolidations, which refers to the closure of an acquired bank in the same neighborhood as an existing FIB branch.

First Interstate spokeswoman Cynthia Lyle says the closed Mountain West buildings eventually will be sold.