Wells Fargo customers are still suffering the fall-out from a computer failure suffered by the US bank on Sunday.
Many may still be struggling to get an up-to-date balance statement, according to reports.
The outage knocked the company's Internet, telephone and ATM (automated teller machines) banking services offline for several hours.
Wells Fargo has not offered many details about the system failure, but it was serious enough that the company had to restore from backup.
"Using our back-up facilities, we restored Internet banking service in about one hour and 40 minutes," the company said in a statement.
"We thank the hundreds of team members in our technology group for working so hard to resolve this problem."
Other banking services such as point-of sales transactions, loan processing and wire transfers were also affected by the outage.
Though customers couldn't perform transactions during the outage, the company's web site was not knocked offline, according to data from web analysis firm Netcraft.
"We apologise for the inconvenience this caused them," the Wells Fargo statement said. The company did not return a telephone message seeking additional information about the outage.
With about 160,000 employees, Wells Fargo operates nearly 7,000 ATMs and almost 6,000 stores across the US.
In the UK, the most recent serious outage to affect a bank was Intelligent Finance. Its website was brought late last month following a hardware upgrade.