WASHINGTON — The giant African snail damages buildings, destroys crops and can cause meningitis in humans. But some people still want to collect, and even eat, the slimy invaders.

The Agriculture Department is trying to stop them. Since June, department authorities have seized more than 1,200 live specimens of the large snails, also known as giant African land snails, all of them traced back to one person in Georgia, who was selling them illegally.

The USDA discovered the snails through a tip from social media at the end of June. From that tip, the department seized more than 200 snails from a person on Long Island, New York, who identified the seller in Georgia. The department then interviewed the seller and seized almost 1,000 more snails in Georgia, plus one each in Indiana, Pennsylvania and New York.

Agriculture officials said the investigation was ongoing and they would not identify any of the individuals.

It’s important to capture the snails without delay, authorities say, because they multiply quickly, producing 1,200 or more offspring a year. And the snails, which can grow larger than the size of a fist, have no natural predators in the United States. People are their only threat.

Florida authorities know this all too well. Agriculture officials there are in their third year of trying to eradicate the snails. They were discovered in Miami in September 2011, and they’ve been found on houses, where they eat plaster and stucco to gain calcium for their shells, and in residential gardens, where they tear through plants.

Mark Fagan, a spokesman for the Florida Department of Agriculture, said the agency so far has found 141,000 snails in 26 areas of Miami-Dade County. Luckily, he said, they have not yet progressed into any of the state’s rich agricultural areas. The snails eat 500 types of plants, including most row crops and citrus, so keeping them away is an important investment for the state’s $100 billion-a-year farm industry.

Florida first saw the giant snails in the 1960s, when a boy from Miami was believed to have smuggled some of them in from Hawaii. His grandmother eventually released his snails into her garden — starting an infestation that took 10 years to eradicate.

Fagan said state officials don’t know how the latest infestation started. But people have different reasons for importing the snails. Sometimes they arrive accidentally in luggage or cargo. The USDA believes most of the snails it has seized this year were being collected by hobbyists who wanted them as pets. They are also used in some African religious practices and even in some cosmetic procedures. And some people consider the snails a food delicacy.

Consumption was the apparent reason for one person’s attempt to bring 67 live snails into California in July. U.S. Customs and Border Protection at Los Angeles International Airport intercepted the snails, which were declared by a person from Nigeria, as for human consumption and destined for a location in Corona, California. Customs officers said the person appeared not to know that importation of the live snails into the United States was illegal.

Eating or handling them could be dangerous, government officials said. According to the federal Centers for Disease Control and Prevention, the snails can carry a parasitic worm that can lead to meningitis.

The Agriculture Department said it wants to warn people about the threat. People may not know the live snails are prohibited in the United States, and if those people report that they have them, they won’t face any penalties. Those who knowingly import them illegally could face fines.

“The more people who know about giant African snails and know that they are illegal in the United States, the better we are in keeping them out,” said Wendolyn Beltz, a director in the USDA’s Animal and Plant Health Inspection Service. “If they didn’t know and they are reaching out to us to do the right thing, there will be absolutely no penalties for that.”

It is legal to import frozen giant African snails for consumption in the U.S., and live snails are legal and available in some parts of Europe, as well as other foreign countries, so people may not be aware of the U.S. ban. The snails seized by the USDA this summer came from Britain, the department said.

Dr. Jim Young, an entomologist at USDA who identifies snails and other species intercepted in international commerce, said the best bet is just to be careful when you are abroad.

“Don’t play with snails when you are on vacation,” he said.