HALIFAX -- Nova Scotia's police watchdog has for a second time declared that Clayton Miller, a Cape Breton teenager found dead in a brook after a police raid on a bush party, died of natural causes.

The Serious Incident Response Team issued an unusual media release Thursday stating that "no further investigation" in the case is needed.

It was in response to claims from a Halifax lawyer representing Miller's parents that new evidence raised fresh questions about the teen's May 1990 death near New Waterford, N.S.

Miller was found face down in an ankle-deep stream, roughly 36 hours after police raided a nearby bush party in an area known locally as "The Nest."

SIRT says the family claims the teen was killed by members of New Waterford police.

But two separate 2015 investigations, conducted by SIRT and Nova Scotia's chief medical examiner, concluded that the 17-year-old was drunk when he fell into the stream while trying to run from police.

The reports echoed a series of earlier investigations, all of which concluded Miller's hypothermia death was an accident. The New Waterford police department was cleared of any wrongdoing.

Then in July, lawyer Ray Wagner showed journalists a video of an interview he conducted with Bryan McDonald, who said he had co-ordinated a search for Miller the day after the party.

In the video, McDonald said his team had searched the area where Miller's body was later discovered -- but their initial search turned up nothing. He said if there was a body in the brook, his team would have found it.

On Thursday, SIRT said there had been no search, and the claim was unreliable.

"SIRT has concluded that the information released, when compared to known facts, is not reliable, and that there was no such search conducted as claimed."

It offered six grounds of facts to back up its finding, including records of both the Nova Scotia Emergency Measures Organization and Cape Breton Ground Search and Rescue Team that detail no search that day.

"The individual that was interviewed and provided this information to the Millers is known to SIRT to be elderly and unwell. As a result, SIRT determined an attempt to interview him would be contrary to the public interest. The known evidence shows he is mistaken about his recollection," the agency said.

"SIRT reminds the public of its previous conclusions: 'Clayton Miller was not beaten or killed by anyone."'

The team's executive director, Ron MacDonald, is stepping down this month to head British Columbia's police watchdog, the Independent Investigations Office.

Retired senior Crown attorney John Scott has been appointed interim director, and work is underway to hire a permanent director.