Fraudsters posing as consular officers operated a fake American embassy in the Ghanaian capital Accra for about a decade and printed counterfeit visas, a US official said.
US State Department Spokesperson Mark Toner said no one was believed to have entered the United States with one of the fake visas, which were reproductions based on genuine travel documents the con-men had obtained.
"This fake embassy made and printed counterfeit visas using expired visas as a blueprint," Toner said.
"It's very, very hard to counterfeit US visas these days... and so this operation failed."
According to a State Department release last month, the fake embassy did not accept walk-in appointments and staff would instead drive to the most remote parts of West Africa to find clients.
The "embassy" workers -- actually Turkish and Ghanaian criminal gangsters -- then shuttled prospective clients back to Accra, put them up in a hotel and ultimately bilked them for as much as $6,000 for dodgy paperwork.
A State Department photo of the fake embassy shows a dilapidated, orange-walled building with rain damage, surrounded by a cracked and buckled sidewalk.
Inside, US President Barack Obama's photo hung on the wall. But the "consular officers" were Turkish citizens who spoke English and Dutch.
By contrast, the real US embassy is an imposing, high-end facility in a tony part of Accra, surrounded by tight security and other diplomatic centers.
"The criminals running the operation were able to pay off corrupt officials to look the other way, as well as obtain legitimate blank documents to be doctored," the State Department said.
Asked how the faux-embassy was able to operate so long, Toner suggested it might be because victims were embarrassed to report the crime.
"They were duped, they were conned," he said.
"You don't necessarily go running to the police and say, 'I illegally obtained a US visa and, oh, by the way it looks terrible.'"
It is not known if some fake embassy clients knew it was a sham but were desperate to get to the United States that they paid for its services regardless.
An informant in the case tipped off authorities to a fake Dutch embassy also operating in the Ghanaian capital.
"It's still being investigated and we are awaiting the outcome," Dutch Foreign Affairs Ministry spokeswoman Daphne Kerremans told AFP.