In what police are referring to as an "internal cleansing" of a biker gang, five people have been charged with first-degree murder in the slayings of eight men in southwestern Ontario.

The victims, whose bodies were found in a farmer's field near Shedden, and one of the suspects are all linked to the Bandidos outlaw biker gang, Ontario Provincial Police confirmed Monday.

Police said the men had all been shot, and Det. Insp. Paul Beesley said they may have been killed in several locations.

John Muscedere, among the dead found in a farmer's field in Ontario, is shown in this undated photo taken from a Bandidos motorcycle gang website. (Canadian Press)

"The victims of this crime have been positively identified and are associated [with], or belong to, the Bandidos motorcycle gang," Det. Supt. Ross Bingley told a news conference in London.

"This is an isolated incident with ties to the Bandidos."

Among the four men and one woman from Ontario who are charged is Wayne Kellestine. Police say Kellestine is a full member of the biker gang.

Also dead in Ontario's worst mass murder is Francesco Salerajno, shown in this undated photo also taken from a Bandidos website. (Canadian Press)

His house was only a few kilometres from where the bodies were found in four abandoned vehicles Saturday morning.

The field is near Shedden, about 30 kilometres southwest of London and 200 kilometres west of Toronto.

Police raided Kellestine's house on Sunday. All the suspects were arrested inside his home, police said.

Police block off an area under investigation near Shedden, Ont., on Saturday. (Steve Martin/Canadian Press)

No other motorcycle gangs are being investigated, they said.

"There's nothing to indicate that there's anything outside the Bandidos ...this is simply an internal cleansing," said Det. Insp. Don Bell.

The six Ontario people found dead are believed to be full members of the gang. They are:

• George Jesso, 52, of Etobicoke.
• George Kriarakis, 28, of Toronto.
• Luis Manny Raposo, 41, of Toronto.
• Francesco Salerajno, 43, of Toronto.
• John Muscedere, 48, of Chatham.
• Paul Sinopoli, 30, of Sutton.

The two other victims are Jamie Flanz, 37, of Keswick, whom police said was a "prospect member" of the Bandidos, and Michael Trotta, 31, of Mississauga, described as an "associate member."

Those charged are:

• Kellestine, 56, of Dutton.
• Eric Niessen, 45, of Monkton.
• Kerry Morris, 56, of Monkton (the lone woman charged).
• Frank Mather, 32, of Dutton.
• Brett Gardiner, 21, of no known address.