Brian Dunn speaks during a keynote speech on the opening day of the Mobile World Congress in Barcelona, Spain, Monday, Feb. 27, 2012. (Photo Credit Denis Doyle/Bloomberg/Getty Images)

An "inappropriate relationship" with a woman employee was behind the abrupt departure of Best Buy CEO Brian Dunn,   the Star Tribune reported, citing a source close to the company.

The newspaper said that, Dunn, who is married, was being investigated by the board of directors for the use of company resources to carry out an inappropriate relationship.  On Tuesday night, Best Buy said that Dunn stepped down before the conclusion of an investigation involving "personal conduct" but no further details have been provided.

"We're not commenting on any details of investigation," a spokesperson for the board told ABC News. "The investigation is ongoing. We just don't have any additional comment at this time. The board findings will be made public and appropriate action will be made at the time if warranted."

The findings from the board are expected to be released within the next few weeks, a source told ABC News.

Dunn had a 28-year career at Best Buy Co., rising up from the sales floor to CEO before his abrupt resignation on Tuesday.

The news of a personal probe sent shock waves through the business community.  Early on Tuesday, the company reported Dunn's decision to step down was a "mutual agreement." Only later did they disclose the probe.

In a statement late on Tuesday, the company said, "Certain issues were brought to the board's attention regarding Mr. Dunn's personal conduct, unrelated to the company's operations or financial controls, and an audit committee investigation was initiated. Prior to the completion of the investigation, Mr. Dunn chose to resign."

The investigation was first reported by The Star Tribune of Minneapolis.

Early on Tuesday, Dunn said in statement that at his departure the company was in position for a "strong future." Dunn, who never graduated from college, became the third CEO of the company in 2009 after joining the electronics retailer in the 80s.  He is the father of three sons.

In the same statement,  the company wrote, "there were no disagreements between Mr. Dunn and the company on any matter relating to operations, financial controls, policies or procedures. There was mutual agreement that it was time for new leadership to address the challenges that face the company."

The departure of the company's CEO comes at a time when it's suffering as online competitors such as Amazon take a bite out of profit.

In March, Best Buy announced restructuring plans after weak quarterly results. The chain made plans to trim 50 of its 1,100 stores and lay off another 400 employees to cut costs.