Peru is the No.1 source of US dollar counterfeiting in the world, overtaking Colombia for the past two years, says the U.S. Secret Service, protector of the world's most widely traded currency, ABC News reports via AP.

In the last 10 years, Peru has increasingly become more productive when it comes to US dollar counterfeiting. $103 million in fake U.S. dollars "made in Peru" have been seized in the last decade, nearly half since 2010, Peruvian and U.S. officials say, AP reports.

The process that sets Peru apart is that each fake US dollar bill is finished by hand. Other counterfeiters around the world rely on sophisticated late-model inkjet printers.

"It's a very good note," said a Secret Service officer at the U.S. Embassy. "They use offset, huge machines that are used for regular printing of newspapers, or flyers."

"Once a note is printed they will throw five people (on it) and do little things, little touches that add to the quality," he said, speaking on condition he not be further identified for security reasons.

The fake counterfeited dollars head mostly to the United States but is also smuggled to nearby countries like Argentina, Venezuela and Ecuador, said Col. Segundo Portocarrero, chief of the Peruvian police's fraud division. Only $100 bills get shipped by counterfeiters to the United States, while $10s and $20s are sent to Peru's neighbors, Portocarrero said.

US dollar counterfeiting in Peru has also improved recently.

"It's much more profitable than cocaine," said a top investigator on Portocarrero's team, noting another of Peru's illegal exports.

Counterfeiters earn up to $20,000 in real currency for every $100,000 in false bills they produce after expenses, the investigator said.

Meanwhile, Washington's decade-long Plan Colombia program became more strict with drug traffickers as well as other criminals, perhaps making dollar counterfeiters turn to Peru instead Portocarrero speculated, AP reports.

AP also notes that Peru has meticulous criminal craftsmen, cheap labor and, by some accounts, less effective law enforcement, all resulting in the ability to get away with making fake US cash.