The embassy operated three days a week and was staffed by English and Dutch-speaking Turkish citizens who posed as consular officers, according to the State Department.
The operators were able to obtain Ghanaian passports with valid but expired US visas that they used as templates to make fake visas, Toner explained.
"No visa that was obtained through this fraud scheme was ever used to enter the United States," Toner told reporters.
Toner did not rule out the possibility that investigators could at some point identify a handful of people who were stopped at a US border.
The United States has launched an anti-fraud operation to determine where similar schemes may exist, Toner added.