Two men have been interviewed by police after a drone was seen flying over the central Melbourne prison where disgraced Cardinal George Pell was being held.

But police believe the drone was being flown as part of a "commercial operation" when it was spotted above Melbourne Assessment Prison on January 9.

They have concluded their probe and referred the matter to the Civil Aviation Safety Authority.

Reports emerged earlier this month that Pell had been moved from the assessment prison on the fringes of the Melbourne CBD to a high security facility in regional Victoria after the drone was spotted near a visitors' garden.

Police interview pair after suspicious drone flight near George Pell's jail_1
Inset: Barwon Prison, about an hour from Melbourne, where Pell is now thought to be held. Photo: AAP

Pell was reportedly moved to Barwon Prison, near Geelong, where he will  count the likes of drug lord Tony Mokbel, bikies and killers as neighbours.

Pell had been held at the assessment prison for almost a year, after his 2018 conviction for sexually assaulting two teenage choirboys at Melbourne's St Patrick's Cathedral in the mid-1990s.

It had been speculated that the drone might have been an attempt to try to get pictures of Pell, which could be worth a significant sum.

A CASA spokesman said the authority was looking at potential safety issues relating to the drone but had made no determinations yet.

It is illegal to fly a drone within 120 metres of a prison or youth justice facility. Doing so can result in up to two years' jail.