However, an expert from the University of Ballarat has a differing view.

A giant hole opened up in a vacant lot in Ballarat East earlier this week. A similar hole has developed at the Brown Hill Reserve, both traditional mining areas.

But council believes it is a sinkhole, not a mine shaft.

Manager infrastructure operations at the City of Ballarat Leigh Ditchfield said it appeared to be a sinkhole and ruled out an abandoned mine shaft.

''It is a depression that has been caused by a fair amount of rain from a hole that has been filled in for 50 or 60 years,'' Mr Ditchfield said.

''There has been years of below average rainfall and when it rains like this, if there's nothing to support it then it can sink in.''

Mr Ditchfield said sinkholes could be created from former tree stumps that had been removed, with the holes having been filled in with soil or wood.

Head of school of science and engineering at the University of Ballarat, Dr Kim Dowling, said it was unlikely that sinkholes would appear in Ballarat.

''It's a very odd environment for a naturally occurring sinkhole,'' Dr Dowling said.

''I've never heard of sinkholes in this area. The rocks (around here) are a bit wrong for that type of activity . . . sinkholes occur more in limestone rocks.''

She said the fact both holes had appeared in mining areas led her to believe they were old mine shafts.

''Ballarat has got such a rich mining history. In the 1850s people didn't disclose where their mines were, so people just don't know about them.

''Until further tests are conducted, it is difficult to say exactly what it is.''

Mr Ditchfield warned people to avoid the holes if they found one and to contact the council immediately.