Some Bank of America customers weren't able to access their online banking accounts on Friday because of an internal systems issue, a person familiar with the matter said.
The second-largest US bank by assets is working to address the problem, said the person, who wasn't authorised to speak on the record. The disruption was not caused by hacker attacks, the person said.
Since last fall, US bank websites have faced a blitz of "denial of service" attacks in which hacker activists disrupt operations by flooding them with information.
Customers logging into Bank of America's website on Friday received a message that said the site was "temporarily unavailable." Some customers took to Twitter to vent their frustrations.
The Charlotte, North Carolina-based bank in October 2011 blamed nearly a week of access problems on heavy traffic and an ongoing systems upgrade. Bank of America says it has 30 million active online banking customers.