The documents found in Fort Simpson, N.W.T., contain detailed information about patients' mental health and history of drug use, including applications to addictions treatment facilities, progress reports from those facilities, and detailed notes from one-on-one counselling sessions.
The files also included social insurance, treaty and health card numbers.
"[These are] clearly very sensitive documents and they shouldn't have been out there," said Elaine Keenan Bengts, the N.W.T's information and privacy commissioner.
On Friday, Keenan Bengts said she knew very little about the situation. But she said it, and the stolen laptop breach this past summer that she's still investigating, constitute as "major breaches."
Julie Green, MLA for Yellowknife Centre, said on Friday that she asked Health Minister Glen Abernethy to investigate why the documents were in the landfill. She wants him to report back to MLAs and the public, and inform the people whose data has been breached.
MLA Julie Green says she requested for the health minister to investigate the breach and report back to the public. (Randall McKenzie/CBC)
"I think there is confidence in the health records system, but there have been a number of privacy breaches," said Green.
"I think that people are aware of those and they're concerned about them."
The health minister has committed to fulfilling those requests, she added.
The Northwest Territories Health and Social Services Authority published a Q&A after CBC News ran the story on Friday.
"Our first priority is to recover these records," said the authority, which added that it's asking the Fort Simpson man to return the files "to prevent further breaches."
The authority says it takes the privacy of residents "very seriously."
It says it will contact the individuals impacted by the privacy breach after it retrieves and assesses the documents. It warns that it may not have answers for residents who contact the authority with questions, until after the investigation.