An Alberta man has been charged with three counts of mail theft following an investigation into missing passports.

The 30-year-old man from Airdrie, north of Calgary, appeared in provincial court on Tuesday.

Police allege the man stole mail while working at a business located at the Calgary International Airport.

"This business was not in a direct relationship with Canada Post," Calgary police said in a release.

Calgary police, RCMP, Canada Post inspectors, as well as immigration and passport officials began the investigation in February 2008 after several customers complained about passport applications that went missing after being sent through the mail.

"Mail items which have been recovered as part of the investigation will be forwarded to customers with a letter of explanation from Canada Post," police said.

More charges may be laid, police added.

The maximum penalty for mail theft is 10 years in prison, according to Calgary police.