The number of drug-trafficking “mules” being foiled at the country's airports has spiked in recent months. A mule is slang for a person who trafficks drugs on their person, often in their stomachs or rectums, as they cross borders.

Most were foiled by their own bodies rather than by any action the police took. Hamilton Keller, a 22-year-old U.S. citizen on his way to Miami, nearly died March 13 after 65 wrapped cocaine pellets began to explode in his stomach. He had to have them surgically removed from his stomach and throat after Drug Control Police arrested him.

“It seems the young Hamilton was trying to travel to the United States and, minutes before leaving, he started to convulse inside the plane, at which time Drug Control Police agents stationed at the airport were informed,” a court press release states. “He was promptly transferred to a hospital.”

Keller joins at least three other mules – another American, an Italian and a Spaniard –whose plans fell apart at the Juan Santamaría airport in Alajuela, northwest of San José city, in the last few months.

Police busted Chercocles, a Spaniard, on March 19 with 2.5 kilograms of cocaine hidden in tuna cans, Fiedrick, a 44-year-old U.S. citizen, on March 6 with 111 cocaine pellets in his stomach and Madonía, an Italian who vomited 77 cocaine pellets, on Feb. 19. Fiedrick was also hospitalized after convulsing and vomiting.

They have all been ordered to three months of preventive prison and are facing up to 20 years in prison if convicted.

Public Security Ministry spokesman Jesus Ureña said the tactic of wrapping drugs in cut-off fingers from latex gloves, swallowing them, and then defecating them later in their country of arrival is a relatively common practice.

“We've seen the trend for about 14 years,” he said. “Normally, they're trafficking networks. But these ones we're seeing are poorly trained, so we suspect they're doing it on their own behalf without a network behind them.”