Two police officers investigating the so-called "Surrey 6" slayings have been suspended over allegations one of them had an inappropriate relationship with a witness.

The investigation involves the October 2007 murders of six men in Surrey, B.C. -- two of them innocent bystanders, the rest with links to gangs.

In January, the RCMP launched an internal investigation after allegations first surfaced that an officer working on the case was involved in an unprofessional relationship with a witness. In February, the Mounties referred the case to the Ontario Provincial Police to ensure the impartiality of the investigation.

RCMP announced Tuesday that based on preliminary findings by the OPP, the sergeant allegedly involved in the relationship and a supervisor have been suspended with pay.

"Based on the information that surfaced, it was felt that suspensions were warranted against two of the officers," said RCMP Chief Superintendent Janice Armstrong.

She said a co-worker is also being investigated, though the allegations against the co-worker and the supervisor do not include having an inappropriate relationship with the witness.

Armstrong declined comment on the exact nature of the allegations against the two, though she added the co-worker is in the midst of a transfer to a new unit to protect the integrity of the case.

Mounties said in February that the witness did not provide any information used by prosecutors as grounds for criminal charges in the case. Armstrong said she's not aware of any changes to that statement.

The two suspended officers are not the only ones who've been relegated to the sidelines while investigating the Surrey 6 case.

RCMP said in January a member of the force was charged with fraud and attempted fraud over a pair of overtime claims he submitted while working on the case.

Armstrong said she doesn't believe the incidents have put a black eye on the police investigation.

"I would certainly say it's never good when the waters get muddied, then we have a tendency to focus on that as opposed to what the investigation's all about," she said.

"What we need to do in these particular cases, if there are issues, if there is inappropriate behaviour, we need to identify that, we need to investigate it."

The killings were discovered in a Surrey high-rise apartment building two and a half years ago.

A haz-mat team made the discovery after neighbours complained of a foul, gas-like odour.

The victims included 22-year-old Chris Mohan and 55-year-old gas fitter Ed Schellenberg, both of whom were unlucky enough to be at the wrong place at the wrong time.

One man, Dennis Karbovanec, pleaded guilty in April 2009 to three counts of second-degree murder and conspiracy to commit first-degree murder in the slayings.

James Kyle Bacon, Quang Vinh Thang Le, Matthew James Johnston, Cody Rae Haevischer, and Sophon Sek are also charged in the case.

A B.C. Supreme Court judge ruled earlier this month that Bacon's charter rights while in jail have been repeatedly violated since his April 2009 arrest, constituting cruel and unusual punishment.

Justice Mark McEwan said authorities at the Surrey Pre-trial Services Centre have been basically acting as agents for police.

Bacon, one of a trio of brothers who police contend are the nucleus of the Red Scorpions gang, is accused of first-degree murder and conspiracy to commit murder in the Surrey 6 case.

His petition to the court said he was allowed only one sheet and a thin blanket, with no pillow, and that the lights in his cell were kept on 24 hours a day. He said he was not allowed access to the prison gym, and that he was denied a television set or gaming console.

Bacon complained that he was denied any visitors or phone calls except with his legal counsel, and that all his mail was read and sometimes photocopied and provided to police.

It emerged during the court hearings that at one point Bacon's privileged telephone calls with his counsel were accidentally recorded on an automatic prison telephone recording system.

"These conditions would be deplorable in any civilized society, and are certainly unworthy of ours," McEwan said in his ruling. "They reflect a distressing level of neglect."