Chase bank and credit card customers have received an apology from the bank for last week's website outage, when the Chase website was inaccessible for more than 24 hours.

The bank's website went dark the evening of September 13, with customers receiving a message stating Our website is temporarily unavailable. We're working quickly to restore access. Please log on later." Service was finally restored around 1:00 a.m. September 15.

We recently experienced a service interruption that affected the website and mobile services, and we apologize if this created any difficulties for you, the bank said in an email sent to its 16.5 million customers over the weekend. We have resolved the problem, and want to assure you that your account information was not compromised as a result of this outage.

The bank assured customers that all account and confidential information remain secure and were not affected by the outage. The bank did not say what, exactly, caused the problem only that it was an internal issue.

According to Bank Info Security, a website dealing with security issues in the banking industry, the outage may point to underlying issues with outdated, legacy technology.

A bank spokesperson says customers who were assessed late fees because of non-payment of online bills during the outage should contact the bank.