A Washington state sheriff’s office says it has solved the mystery of nearly two dozen dead canines who washed ashore recently.

The animals were foxes being used legally as bait for fishing operations, the Skagit county sheriff’s office said on Friday.

The agency’s announcement came after local residents had been shaken by the discovery of the carcasses along the shoreline of Guemes Island in late March and early April. The island is about 80 miles (130km) north of Seattle and home to about 600 residents, and investigators had to conduct necropsies due to the state of the bodies.

The carcasses were deteriorated, with some of the bodies missing fur and paws, making it unclear initially what type of canines they were.

Authorities told local news station KOMO News that the carcasses probably ended up in the water due to a mechanical problem that led to cargo going overboard.

The sheriff’s office said the carcasses were lawfully purchased and transported to the state. The responsible party has been contacted and is cooperating with the ongoing investigation, according to the agency.

“Given the facts and circumstances known, the sheriff’s office does not anticipate referring any charges to the prosecutor’s office,” the agency’s added in a statement.

Local residents had reported being horrified over the discovery, likening it to “the start of a horror movie”.

“It’s a creepy mystery out here,” said Olivia Cole, the fire chief of Guemes Island.

Ellen Fitch, who found some of the carcasses, told a local news station that other residents were starting to make assumptions about what had happened to the canines. She recalled hearing rumors such as “they found wolves and foxes and coyotes” – or “there were witches involved”.

Fitch said: “They’re just exaggerating.”

In an email to the Seattle Times, Lt Jeff Willard from the sheriff’s office said that the foxes were purchased as bait for crabbing.

More common sources of crab bait are the head of oily fishes, such as mackerel and salmon, for their scent, and other sources of protein including chicken and turkey. Because crabs are scavenger feeders looking for protein sources, typically any kind of “stinky” carcass works as bait.