MIAMI

At a little-known government laboratory in South Florida, they keep the snails under lock and key. Sure, any escape would be sloooooow. But giant African land snails are such a threat to humans that the rules say they have to be kept locked away, just in case.

The aptly-named snails can grow to be more than 6 inches long. Wherever they go they leave a trail of smelly excrement. They eat 500 kinds of plants. They produce up to 500 eggs two or three times a year, and because they're hermaphrodites they don't need a mate. If they aren't getting enough lime from the soil for their shells, they will gobble the stucco off the side of a house.

They also carry a parasite that can infect humans with meningitis.

Florida officials often don't know for sure how an invasive pest gets loose in the state — the pythons taking over the Everglades, for instance. But they are pretty sure the giant African land snails that the state has spent more than $6 million to capture and kill were smuggled in by a religious cult that used the snails' mucus in healing rituals.

So far, though, prosecutors have not charged them with anything. Miami's most prominent practitioner of Santeria predicts they never will. He also says the government needs to check Tampa, Orlando, Jacksonville, West Palm Beach and Tallahassee for snails.

"The potential is higher in those areas," said Oba Ernesto Pichardo, of the Church of Lukumi Babalu Aye in Hialeah. "All those areas have sufficiently active religious populations."

According to court documents, the man who brought the snails to Florida is Charles Stewart, of Hialeah, sometimes known as "El Africano" or "Oloye Ifatoku." Stewart practices a traditional African religion called Ifa Orisha, which is often confused with the Cuban Santeria.

In January 2010, state and federal officials raided Stewart's home and found at least 20 of the giant snails in a wooden box in his back yard. He told them he had smuggled them from Africa in his luggage. He had help — a priestess known as "the Godmother" had slipped some snails into the United States by hiding them under her dress on a flight from Nigeria.

Stewart's followers told investigators he would crack off part of a snail's shell and pour the mucus into their mouths to provide them with good health. The followers then became violently ill, according to court records.

Officials announced they were investigating what Stewart had done but at that point said there was no sign the snails had gotten loose. A year later, though, two sisters who lived 8 miles from Stewart's home notified state officials that their back yard was infested, and that touched off a major eradication effort.

Three years later, the state Department of Agriculture has killed more than 151,000 of the snails from suburban yards scattered around the eastern side of Miami-Dade County and recently fielded its first reported infestation in Broward County.

Just finding them can be a chore. Native Florida snails, which are far smaller, live on trees. Giant African land snails live on the ground, or under it, said Mary Yong Cong, the scientist in charge of studying the snails for the state Department of Agriculture and Consumer Services.

If conditions are too dry, they burrow into the soil and hide. When the rainy season returns, they emerge, like zombies clawing their way out of a grave.

Recently, Agriculture Commissioner Adam Putnam touted his agency's acquisition of a pair of Labrador retrievers trained to sniff out the pungent scent of the snails' excrement. Cong keeps live snails locked in her lab at the U.S. Department of Agriculture's Subtropical Horticulture Research Station in Miami so the dogs can become familiar with the smell.

"We're paranoid about them escaping," she said, holding up a large one that's named David, after the state employee who caught it.

Despite the massive resources committed to catching the snails, there has apparently been no further pursuit of the man suspected of bringing them to Florida. A spokeswoman for the U.S. Attorney in Miami wouldn't even confirm the existence of an investigation.

Stewart, in a brief interview, said he didn't want to talk about it either. Asked whether the government investigation into his activities was over, he said, "I have no idea. I have no comment."

Pichardo suspects the investigation has moved at a snail's pace because of a U.S. Supreme Court case from 1993 — one he knows well.

After Pichardo launched his Santeria congregation in Hialeah, the Church of the Lukumi Babalu Aye, the city passed an ordinance banning the animal sacrifices that are one well-known rite of the religion. Pichardo fought the city all the way to the U.S. Supreme Court. In 1993, on a 9-0 vote, the high court ruled that the ban violated the church's right to freedom of religion.

Given that ruling, the government knows it must tread lightly in any potential criminal case involving animal sacrifice, even when the sacrifice is a smelly mollusk that makes people sick, Pichardo said. Stewart had no bad intent, he contended, and thus should not be charged.

He pointed out, however, that his own church steers clear of the giant snails. "We do use some Florida land snails in a very few, very limited rituals," he said, "but they are never consumed."

Staff researcher Caryn Baird contributed to this story, which contains information from the Miami Herald and Wall Street Journal. Contact Craig Pittman at craig@tampabay.com. Follow @craigtimes.