An Ontario agency tasked with improving cancer care says test results for almost 6,500 people may have been lost in the mail.
Cancer Care Ontario says it is investigating whether 15 reports containing patients' personal information were successfully delivered to doctors in February and March.
The agency used Canada Post's Xpresspost courier service to mail the reports, which included the names, health card numbers and colon cancer screening results for 6,490 patients.
Canada Post was supposed to send the packages back to the agency if it couldn't get a signature upon delivery.
Cancer Care Ontario says Canada Post admitted earlier this month that some of the reports were delivered without a signature confirmation.
The agency says it is also looking into the delivery status of 11 additional screening reports with information on 5,440 more people.
The office of Ontario's privacy commissioner says it's checking whether there was a privacy breach for the near-12,000 patients included in the reports.