Canyon Mansfield, a 14-year-old boy in Idaho, was walking his dog Casey near his house when he came across a small device embedded in the ground at the boundary of his family’s property. It looked like a sprinkler, he later told a local news reporter, and when he touched it, it popped, emitting an orange powder. The powder blew into Casey’s face, causing the dog to convulse and, a few minutes later, die.

The device Canyon triggered was an M-44 trap, placed there by a representative of the U.S. Agriculture Department. The orange powder was sodium cyanide. When it came into contact with moisture in the dog’s mouth, it created hydrogen cyanide gas.

Every few years, someone’s dog stumbles onto one of the traps and is killed, generating headlines. There was Max, a 2-year-old German shepherd killed by an M-44 trap in Utah in 2006. In 2011, a pit bull named Bella was killed by a device in Texas that was placed less than a thousand feet from the home of the dog’s owner. (Fair warning: That link shows an image of the dead dog.) In 2003, a guy near Bonanza, Utah, found an M-44 and picked it up. It detonated, spraying him with cyanide powder. He lived.

The USDA tracks the number of accidental “takes” from M-44 traps each year. Since 2008, 464 dogs have been killed by such traps, 230 of them unintentionally. That’s feral dogs, mind you, which is why some of the deaths are listed as intentional. Data on the number of domestic livestock and pets killed by M-44 traps goes back only to 2013. Over that time, 22 animals have been killed. Seven died in 2016, all of them in West Virginia, according to USDA data.

Overall, more than 300 animals were unintentionally killed by M-44 traps in 2016, including 180 foxes, 30 opossums, 57 raccoons, 21 skunks, two ravens and a black bear. The traps specifically target predatory animals. While most of the trap is buried, the part that remains above ground is wrapped in bait, which triggers a “bite and pull” reflex from an animal. When the predator tugs at it, the powder is deployed.

Obviously, pet dogs are not an intended target. The traps are generally placed to eradicate coyotes, more than 100,000 of which have been killed by the devices since 2009.

The USDA has a lengthy set of instructions detailing how the traps should be deployed. They are authorized for use only against wild canids (dogs, coyotes and the like) that either are suspected to carry disease or are targeting endangered animals or livestock. Each device must be inspected weekly and should be marked with bilingual signs warning people of their presence.

Canyon’s father told East Idaho News that his son didn’t have any warning. “We didn’t know anything about it,” he said. “There were no neighborhood notifications. Our local authorities didn’t know about this.” Only 50 yards from the device that killed Casey, the family discovered a second M-44.

It’s not clear how many M-44 devices have been placed throughout the country or where. (The USDA did not respond to a request for that data by the time this article was published.) Kara Clauser of the Center for Biological Diversity gathered data on the states where animals were unintentionally killed by M-44 devices; they are mostly clustered in the west but include deaths in West Virginia and Virginia.

After the death of Casey, a man from American Falls, Idaho, wrote to the Idaho State Journal to express his opposition to M-44 traps.

“The idea that I could be enjoying the backcountry — or, apparently, country much closer to my home — and stumble across a land mine, courtesy of, that shoots cyanide up the face of my dog, me, my wife, or my companions is shocking to me,” Phil Bregitzer wrote. “I don’t think these should be used, and I’ve written my state and federal representatives to express my opinion. I encourage others to do the same.”

Bills have been introduced in Congress on several occasions to ban M-44 devices, including in 2007 and 2012. Neither of those bills even went to committee.