An Ottawa couple was charged with extortion Friday after a year-long investigation by the Ottawa Police Service.

Police said Ali Karimi and wife Nava Vosough, owners of a chain of Centretown convenience stores, falsely accused two former employees of theft.

According to police, the employees, two male international students, age 24 and 38, respectively, were forced under duress to pay money to the couple. Police allege the couple told the employees they would call immigration officers and the police if the two men did not pay them the money.

There were two other attempts at extortion, police said, involving a relative of one of the employees and another former employee.

Ali Karimi, 42, has been charged with two counts each of extortion, criminal harassment, theft over $5,000 and forcible confinement, as well as other related crimes.

Nava Vosough, 29, was charged with two counts each of extortion, criminal harassment and theft over $5,000, as well as three counts of intimidation and other related crimes, including assault.

Police said Friday their investigation of the couple began April 29, 2007, and concluded February 15, 2008. Police say they suspect there may be additional victims of extortion and an investigation into those incidents is ongoing.