The move came after Pope Francis, earlier this year, issued new procedures for the handling of sexual abuse and cover-ups, including that bishops be held accountable for past actions.
Dunedin Bishop Michael Dooley, contacted overseas, confirmed the move yesterday, but said the National Office of Professional Standards (NOPS) - part of the Catholic Church in New Zealand - was also involved.
"I am waiting to hear back from NOPS once they get a notification from the Vatican about the next course of action."
It was not yet clear whether the Vatican could launch its own investigation, or direct the NOPS to do so, but it was understood the focus was on what Bishop Kavanagh knew, and what he did, when allegations of sexual abuse first emerged.
Cardinal Dew is also overseas, and a spokesman for the New Zealand Catholic Bishops Conference declined to comment yesterday.
NOPS director Virginia Noonan also declined to comment.
Confirmation of the Vatican's involvement came after ODT Insight, in its Marked by the Cross series, revealed significant offending by priests, religious brothers and lay teachers within the Catholic Diocese of Dunedin, much of it dating back decades.
That included the actions of a former Catholic priest, Magnus Murray, whose offending against boys in Dunedin - from the 1950s to the 1970s - was brought to Bishop Kavanagh's attention in 1972.
The investigation showed Bishop Kavanagh had moved Murray to Australia, and later allowed him to resume public ministry in the North Island, where more victims have since emerged.
Murray was eventually forced into retirement in 1990, as fresh allegations emerged, but retained his title as a priest even after he was eventually convicted of offences against four Dunedin boys in 2003.
He was only finally defrocked by the Vatican earlier this year, after the matter was referred to the Vatican by Bishop of Hamilton Steve Lowe.
Bishop Kavanagh's defenders have insisted he acted according to best practice at the time in dealing with Murray, but others - including survivors and their supporters - have criticised his actions and his ignorance of other past abuses.