Canada Post says it is investigating the disappearance of 54 passport applications from Kelowna. (Mike Laanela/CBC)

More than 50 passport applications filed in B.C. have gone missing along with some personal documents, and the federal agencies involved say they have no idea how or where they disappeared.

Forty-three of the missing applications were filed at the Service Canada office in Kelowna, in the interior of B.C., and were on their way to a Passport Canada office via Canada Post when they disappeared.

But 11 of the applications were from people who applied for their passports directly by mail to Passport Canada and had to include their birth certificates and other sensitive documents, which have now been lost.

Canada Post spokesperson John Caines told CBC News that the 43 applications sent from the Service Canada location were last seen on March 27, when they were shipped from the Kelowna office. The other 11 applications were last accounted for on the same day at the Canada Post office in Kelowna.

"Well, we are not sure what happened," said Caines, "We certainly take responsibility for anything that's in the mail stream. Where this went out of the mail stream, or where it went missing, we don't know. We're hoping we are going to find out what happened, and we are going to make sure it doesn't happen again."

The RCMP and the three federal agencies are involved in the investigation to find out where and how the sensitive documents went missing. This isn't the first time a large number of passport applications have gone unaccounted for.

A total of more than 150 have disappeared in the last two years, including more than 50 applications from southern B.C. and Alberta that were last seen at a Canada Post facility in October 2008.

That case prompted a warning from Canada's privacy commissioner who citied concerns about identity theft and warned that changes must be made to increase security. The federal agencies involved have struck a task force to look into those concerns.

Passport Canada spokesman Sébastien Bois said Kelowna is one of seven cities in the country involved in a pilot program that allows people to apply for a passport in person at a Service Canada office.

"Employees of Service Canada will look at your birth certificate or Canadian citizenship card, and they will give it back … so at least most of these people did not have their birth certificate lost in the mail," said Bois.