The Royal Newfoundland Constabulary is under criminal investigation by an external agency, CBC News has learned.

The probe is being conducted by the Serious Incident Response Team (SIRT), a civilian-led agency from Nova Scotia that investigates serious incidents involving police forces.

"This is a criminal investigation, so certainly criminal charges are a potential outcome," said Ron MacDonald, a lawyer and civilian director of SIRT who is leading the investigation.

MacDonald stressed that his team has experience with this type of investigation in Nova Scotia.

"I don't owe allegiance to anyone in this matter," he said. "At the end of the day we will make the right conclusions based on the facts of the case."

Investigation focused on handling of informant

MacDonald would not comment on any specifics of the case.

Neither would top justice and law enforcement officials in Newfoundland and Labrador.

But CBC News has learned that the investigation involves senior RNC managers, and is focused on their use of a criminal as an informant during a high-level investigation.

The informant was supposed to provide the RNC with information it needed to crack its case. But sources say the informant continued to commit crimes without being arrested — even though some of the incidents were witnessed by police officers.

This was allowed to continue for a period of several weeks until the informant assaulted and injured two people and was finally arrested.

Nova Scotia's Serious Incident Response Team is investigating a complaint involving the Royal Newfoundland Constabulary. (CBC)

The RNC won an injunction in Newfoundland and Labrador Supreme Court Tuesday barring CBC from publishing the story.

Justice Donald Burrage partially lifted that order late Wednesday afternoon.

The identity of the confidential informant — and any information that would lead to identifying the informant — remain subject to a publication ban. CBC News did not contest that order, and never had any intention of revealing the informant's identity.

SIRT called in by justice officials

The Department of Justice and Public Safety called in SIRT in November 2015, after receiving a complaint.

"In the circumstances they felt it best that an independent organization outside of Newfoundland conduct that investigation," MacDonald said.

"To ensure that, at the end of the day, the public of Newfoundland could see that this investigation wasn't conducted by other police agencies or by the home agency, but in fact by an independent organization from another province."

​MacDonald and two police officers from outside the province have been interviewing witnesses since December as part of the investigation.

Chief issued statement

Before the police filed a court application Tuesday afternoon to stop the CBC from reporting on this matter, RNC Chief Bill Janes issued a statement.

"The RNC will cooperate with SIRT to enable them to conduct the work required," the chief's statement noted.

"In order to protect the integrity of the investigation we are unable to discuss further details at this time."

Meanwhile, MacDonald described the allegations as raising "significant public interest issues" and noted that his investigation will take several months.

At that point, he will turn over his report and his recommendations to Justice and Public Safety Minister Andrew Parsons.

"I am respecting the investigative process that is currently underway and I am presently unable to comment on the specifics of the allegations that have been brought forward," Parsons said in a statement.

"However, I look forward to addressing this matter once that investigation is complete. It is of paramount importance to this government that the public have confidence in the administration of justice in the province."