Bank of America Corp said an ongoing upgrade and heavy traffic was behind six days of problems with its banking website, easing concerns about possible hacking.

The Charlotte, North Carolina, bank is about halfway through a multi-year effort to transfer customers to a new technology platform, David Owen, head of online and mobile banking, said late Wednesday.

The bank has also been adding new features and experiencing heavy month-end traffic, he said.

Customers have had trouble accessing accounts since on Friday.

The bank posted Web notices warning customers of slowness. A spokeswoman has noted, without citing a cause, that the problem was not the result of hacking or malware.

There is nothing that points to a third-party intervention, said Owen. The bank has consulted with law enforcement authorities and outside experts.

As of Wednesday, the bank's site was operating normally, but officials are taking things day by day, he said.

The conversion to the new technology platform started two or three years ago and has about two more to go, Owen said.

(Reporting by Rick Rothacker in Charlotte, North Carolina; Editing by Richard Chang)