TORONTO - The mysterious appearance of two dozen precariously balanced rock sculptures in a Toronto river was revealed Tuesday to be the work of an artist simply looking to clear his head on a Sunday afternoon.

The spectacle created a splash in the city when the sculptures seemingly appeared out of nowhere over the long weekend. Onlookers at the Humber River applauded Peter Riedel on Tuesday when he made a reluctant appearance at the site.

Residents who did not see Riedel assembling the pieces were baffled to find his mysterious work there and had several theories over who could have left the formations, and when.

Some speculated a group of people, working under the cover of darkness, was responsible.

The sculptures, Riedel said, took about four hours to create from flat rock he found in a shallow part of the river.

"I come, I do my thing, and I leave. I don't leave any signature so to speak," Riedel said.

"It's kind of fun that it is mystery for people, and not about me so much in my own mind."

Riedel -- a self-taught artist -- said he is happy people enjoy his work, but he makes sculptures solely to clear his head and has not sought any attention over the past five summers he's been making them.

Several residents out to view his work were convinced the sculptures had a little bit of help to stay together for so long.

"Looking at how they are balanced, some of it doesn't quite make sense without the additional bit of crazy glue to make it stick," said Wilf Martini who was out for a walk with friends.

He and dozens of other onlookers were astounded to learn that the rocks were holding up on their own.

Riedel said he washes off algae and other slime, and grinds down the flat part of the stone to help it balance.

"That would be cheating so no, no glue, none, whatsoever. It's just centre of gravity, just balance," he said.

The sculptures, roughly about one-metre tall, were still standing in the river Tuesday afternoon, although Riedel said some of the top rocks have already fallen off.

The rocks are balancing on thin edges, with some large slabs remarkably holding steady on tiny stones.

The sculptures usually remain intact for about three days before they get knocked over by wind or vibrations, Riedel said.

One man thought the work was done by a group of people because some of the stones appear to weigh as much as 20 kilograms.

"It's a fascinating piece of art, and I don't know how one person can do it, it looks like it has to be two people at least. Some of those rocks are really heavy," said Ralph Cowan.

Riedel said he first got the idea after seeing an artist balance rocks in Vancouver. He says the process of selecting balancing stones is calming, and helped him deal with a difficult period in his life.

The fact his creations can easily be knocked over symbolize the way people can be knocked down by adversity they face in life, said Riedel.

"Like so many things in life, the balance isn't always up to us. We think things are perfect and balanced, but sometimes life has surprises for us too," he said.

He likes that even though the stone creations may fall apart, they become a clean slate from which to create again.