CIBC customers can once again use the company's automated banking machines after a software problem knocked about a third of the machines offline.

The problem occurred during a routine upgrade of software in the early morning hours on Wednesday and affected about 1,200 of the bank's 3,600 ABMs across the country, spokesman Rob McLeod said.

"The issue was recognized early on, and it was stopped from infecting a broader part of the network," McLeod said.

The problem was isolated to the individual machines and did not affect the banking network, he added later in an e-mail.

None of the systems inside CIBC's branches were affected, he said.

"The majority of our bank machine network and all of debit, branch, telephone banking and on-line banking were operating normally."

Normal service was restored Thursday morning, McLeod said.

The bank will reimburse service charges for customers who had to use other financial institutions' machines during the outage, he said.