(CNN) -- What appears to be a separated human foot inside a shoe -- possibly the sixth discovered in Canada's British Columbia in the past 15 months -- has been found on a riverbank, Royal Canadian Mounted Police said Wednesday.

Some of the feet found this year washed up on Westham Island, south of Vancouver, British Columbia.

The shoe -- a left New Balance running shoe -- was found about 11:30 a.m. Tuesday on the south arm of the Fraser River by a Richmond, British Columbia, couple, police said.

It was turned over to the British Columbia Coroners Service for examination and DNA testing, authorities said.

Before Tuesday, five feet -- all inside running shoes -- had washed ashore in southern British Columbia since August 2007. One of them, a right New Balance shoe, was found May 22 on Kirkland Island. That foot was determined to belong to a female, authorities said.  View a map of where the feet washed ashore »

The provincial coroners' office said in July that DNA tests determined that two of the five feet -- a right foot found February 8 and a left foot found June 16 -- were from the same male, but they said they didn't know to whom any of the feet belonged.

What was initially thought to be a sixth foot inside a running shoe, found in June, was determined to be a hoax. Authorities said a "skeletonized animal paw" was put in the shoe with a sock and packed with dried seaweed.

"Obviously, due to the fact that a hoax was perpetrated previously and then extensively reported on, we want to proceed cautiously [with Tuesday's discovery] until we know what exactly we are dealing with," said Constable Annie Linteau, an RCMP spokeswoman.

The provincial coroners' service said in July that the five sets of remains found to that point appeared "to have naturally separated (disarticulated) from the body."

There was no forensic evidence, such as tool or trauma marks, on the remains to suggest that they had separated in any way other than decomposition, the service said.

Authorities are investigating multiple possibilities on the origin of the feet, including foul play and the chance they could belong to victims of a plane crash. Missing persons files are also being reviewed.

Four of the five feet discovered between August 2007 and June 2008 were in running shoes made between 2003 and 2004, and the other was made in 1999, according to police. Royal Canadian Mounted Police have released photos of the shoes, hoping someone can help identify the remains.

Here is a timeline of the discoveries in British Columbia, according to police:

August 20, 2007

The first foot is found by an American man and his 12-year-old daughter boating near Jedidiah Island. The shoe is later identified as a Campus brand running shoe, primarily white with blue mesh, and is believed to be a size 12. It is determined that it was produced in 2003 and distributed primarily in India.

August 26, 2007

The second foot is found on Gabriola Island by a resident walking on a trail. The shoe is a size 12 men's Reebok running shoe, primarily white in color. It was produced in 2004 and was distributed globally, though mostly in North America. It was first available March 1, 2004, but is no longer available.

February 2

A third foot is found by two forest workers on Valdez Island. The shoe is a size 11 blue and white Nike running shoe, made in 2003 and sold in Canada and the United States from February 1 to June 30, 2003.

May 22

The fourth foot is found on Kirkland Island by a man walking along the shoreline. The size 7 blue and white New Balance running shoe was made in 1999 and distributed in major retail stores. DNA tests later determine that the remains belonged to a female.

June 16

A fifth foot is found on Westham Island, in the same type of Nike shoe as the foot found February 2. DNA tests later determine that both feet belonged to the same male.
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