The person responsible for "liking" a pornographic clip from the official Twitter account of the Australian Border Force commissioner remains a mystery.
The clip was "liked" from Roman Quaedvlieg's account mid-last year while he was on leave amid an investigation into his personal conduct.
Six departmental staffers had access to his account.
Immigrations officials asked the Australian Commission for Law Enforcement Integrity to look into the curious case and have been handed a final report.
"They found no evidence that Mr Quaedvlieg used the official ABF commissioner's account to 'like' a tweet containing a pornographic clip from an account under the name Lady Mystique," Home Affairs deputy secretary Rachel Noble told a Senate committee on Monday.
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"ACLEI also found no evidence of who had 'liked' the tweet, or whether the 'like' was accidental or intentional."
Ms Noble could not rule out the possibility his account was hacked.
"I think what ACLEI have told us is that they have no evidence one way or the other," she said.
Defence Industry Minister Christopher Pyne blamed hackers for his Twitter account "liking" an explicit pornographic video late last year.
