Global police forces have carried off the largest reptile trade bust to date, arresting 12 suspects and seizing more than 4,000 live reptiles at airports, breeding facilities, and pet stores across Europe, North America, and elsewhere throughout April and May.

The initiative, dubbed Operation Blizzard—a play on words referring to the deluge of activity around lizards—was coordinated by Interpol and Europol in response to the illegal trade in snakes, turtles, and other protected reptiles. Trafficking of these animals is threatening some species with extinction and also fueling disease outbreaks among humans. (See how the exotic pet trade can endanger reptiles.)

The exotic reptile trade has exploded in the past two decades, with millions of the animals now imported—legally and illegally—into the European Union and United States as household pets. Some reptiles are also coveted for their skins, made into high-end fashion items such as shoes, belts, and handbags. (Learn more: The Exotic pet trade, explained.)

Few protections exist for reptiles: Only about 8 percent of the roughly 10,000 species are included in the Convention on International Trade in Endangered Species of Wild Fauna and Flora, the international treaty that regulates the commercial trade of wildlife across national borders.

As part of Operation Blizzard, law enforcement agencies in 22 countries—including New Zealand, Italy, Spain, South Africa, and the U.S.—scoured intelligence reports, cross-referenced earlier cases, monitored social media, and conducted targeted inspections of breeding facilities, says Sergio Tirro, a project manager for environmental crime at Europol who helped collect intelligence for the operation. Sharing intel across borders allowed them to identify more than 180 suspects.

“This operation clearly demonstrates the value of international cooperation” says Chris Shepherd, executive director of Monitor, a nonprofit organization in British Columbia, Canada, dedicated to combating illegal wildlife trade. “It also illustrates the scale of this massive and well-organized trade.”

Six arrests have already been made in Italy and another six in Spain, with further arrests and prosecutions expected, according to a statement from Interpol. In one case, according to Europol, an airline passenger had 75 live turtles in his luggage without any of the required paperwork. (Read more about the illegal turtle trade.)

“Generally, our main target is a not a single passenger or individual—our focus is organized crime groups behind the illegal trade,” Tirro says. Still, many of the individuals identified were small-scale participants rather than organized crime leaders, he notes, adding that law enforcement hopes this work will help them build cases against top-tier people who are coordinating the illegal trade.

The seizures included more than 20 crocodiles and alligators, six Kenyan sand boa snakes found in air cargo in the U.S., and 150 items made from reptile skins—including handbags, watchstraps, traditional medicines, and taxidermied products. Although the main focus of the operation was on reptiles, law enforcement also nabbed other animals and wildlife products: live owls, falcons, swans, elephant ivory, bushmeat.

Nine reptiles being smuggled from Washington State into British Columbia were seized in Canada, says Sheldon Jordan, who heads up the wildlife crime unit of Environment and Climate Change Canada. Three of those animals had died in transit, underscoring how deadly the illegal wildlife trade can be, he says. Operation Blizzard was conducted at this time of year because most reptile trading in the northern hemisphere takes place during the spring and summer months, when these cold-blooded animals are more likely to stay warm enough to survive, Jordan says.

Seizing 4,000 reptiles is significant, Shepherd notes, but “there are millions of reptiles being illegally traded every year,” and the market for these creatures keeps growing. Dismantling the well-organized networks that orchestrate the reptile trade and working with the countries where these animals are stolen from the wild, he says, are essential.