Speaking at the Leveson Inquiry into press ethics, the editor of the newspaper made a distinction between investigators and "search agents".
Mohan said: "Yes, private investigators have been used in the past without the permission of the chief executive officer, but now new controls are in place."
Asked if investigators were used to secure ex-directory telephone numbers, Mohan said: "I'd make a distinction. I've used search agents in the past, but I wouldn't describe them as private detectives."
Of whether such 'search agents' were used now, with or without the permission of the chief executive officer, he added: "Yes, search agents can, there is a distinction."
In his written statement to the inquiry, Mohan said: "The Sun has used private investigators in the past to assist journalists on stories, but I am not aware of any private investigators being commissioned under my editorship.
"The Sun does, however, regularly use news agencies and search agents to trace the addresses and telephone numbers of people we would like to contact in connection with stories."
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He added that these "desk-based individuals or agencies" search publicly-available databases for information, such as Companies House records and electoral rolls.
Mohan added: "It typically costs between £50 and £300 to obtain an address for an individual from such an agency. Last year, The Sun paid approximately £165,000 in fees to a small number of such agents."
In his own witness statement, former editor of The Sun Kelvin Mackenzie said: "As far as I know we never used private investigators but I am certain that public officials would have disclosed important information to us and that depending on what that information was we would have paid them.
"I am wholly supportive of public officials whistle blowing to The Sun even if we have to pay money. After all, the police pay informants to disclose information."