NEW YORK — Best Buy CEO Brian Dunn abruptly resigned on Tuesday after the embattled consumer electronics chain launched an internal investigation into his “personal conduct.”

Best Buy released a statement late Tuesday saying that it is conducting the probe after earlier only saying the departure was a “mutual decision.” The chain would not give any specifics on the circumstances surrounding the investigation of Dunn, a 28-year Best Buy veteran who had been CEO since 2009.

“Certain issues were brought to the board’s attention regarding Dunn’s personal conduct, unrelated to the company’s operations or financial controls, and an audit committee investigation was initiated,” according to a company statement issued late Tuesday. “Prior to the completion of the investigation, Mr. Dunn chose to resign.”

Dunn, who started his career at Best Buy as a sales clerk in the 1980s, could not be reached for comment about the investigation. But earlier on Tuesday, the 50-year-old said in a statement that he was leaving Best Buy poised “for a strong future.”

Best Buy Co. hasn’t disclosed the terms of Dunn’s severance package. But Dunn’s annual compensation for fiscal 2010, the latest figures available, was worth about $5 million — half of what it was in the prior fiscal year.