California Attorney General Bill Lockyer vowed to prosecute wrongdoers at the end of his investigation into whether private detectives hired by HP impersonated board members and journalists to get private telephone records.
Dunn had detectives hired to ferret out who had been leaking information from board meetings to members of the press, according to the veteran Silicon Valley computer company.
Lockyer's office launched an investigation more than a month ago after getting word that telephone records of board members were obtained by a ruse known as "pretexting," calling the telecom company and posing as customers.
"We believe a crime has been committed and we are just trying to find out who did it," Lockyer spokesperson Tom Dressler told AFP on Friday.
"We are aggressively pursuing it. Once we are satisfied we have done a thorough job obtaining evidence, we will decide on enforcement actions."
While no law on the California books specifically outlawed "pretexting," the deception violated laws regarding identification theft and unauthorised access to computer data, Dressler said.
A law awaiting signature by state Governor Arnold Schwarzenegger would make "pretexting" illegal.