TORONTO - Colon cancer screening tests for almost 6,500 Ontario patients have been lost in the mail and the provincial health agency who sent them to doctors' offices says several thousand more could also be missing.

Cancer Care Ontario says 15 reports containing colon cancer screening details for 6,490 patients mailed to doctors in February and March were never delivered.

The provincial agency used Canada Post's Xpresspost courier service to mail the reports, which included patients' names, health card numbers and test information.

Cancer Care Ontario began looking into the delivery status of nearly 7,000 total reports sent out after Canada Post concluded in mid-June that one of the couriered packages was lost, said Pamela Spencer, the agency's chief privacy officer.

It wasn't until earlier this month the postal service told Cancer Care Ontario the 15 packages were not delivered, Spencer said. The agency is currently trying to find out what happened to 11 more deliveries of reports on an additional 5,440 patients.

Spencer says the agency should know by August if those 11 reports have been lost.

Spencer adds Cancer Care Ontario held off on announcing the lost reports until they could check with more doctors in order to narrow down the number of potentially lost reports.

"We have been consumed with our investigation to try to reduce these numbers so that we were not unnecessarily notifying people when in fact those screening activity reports had been received by the physicians' offices," she said.

Canada Post continues to look for the 15 deliveries confirmed missing, spokesman John Caines said.

"We're not giving up on these packages," he said.

Ontario Information and Privacy Commissioner is investigating the incident.

Ann Cavoukian says Cancer Care Ontario should not have sent the reports on paper, but put them instead on secure digital media if they were going to be couriered.

"You can send either a USB key, or just a CD," she said. "You can encrypt that ... so if that falls into unauthorized hands -- doesn't matter, (whoever has it) gets gibberish, they can't access the data."

Anyone who wants to make a privacy complaint can call 1-416-326-3900 or 1-855-545-8989. Complaints can also be emailed to