Many dogs were exterminated following the 1986 Chernobyl disaster to prevent the spread of radiation.

Those who survived continued to reproduce in the wild. Today, hundreds of their descendants roam the Chernobyl Exclusion Zone.

Workers at the Chernobyl power plants have started to adopt the animals, but nuclear experts still warn against petting them, since their fur might contain radiation.

Not all Chernobyl dogs are unsafe pets. Last year, the US welcomed the first round of puppies to ever be allowed outside the exclusion zone.

Visit Business Insider's homepage for more stories.

One of the most chilling moments in HBO's new miniseries, "Chernobyl," takes place on a sunny day after the evacuation of the Chernobyl Exclusion Zone, a restricted area in Ukraine. Hours earlier, the core of a nuclear reactor opened at the Chernobyl Nuclear Power Plant, releasing plumes of radioactive material into the air.

The zone is quiet (residents have already been loaded onto buses and sent to nearby settlements), but the Soviet "liquidators" tasked with cleaning up the disaster are hard at work.

Read more: How dangerous is it to visit Chernobyl? We asked a nuclear-waste expert involved in the cleanup.

A young civilian recruit reports for duty, where he's given his first assignment: to join two other liquidators in shooting stray dogs that patrol the region. Of all the horrors depicted in the series — a fatal helicopter crash, the death of a just-born baby, people's flesh peeling off due to acute radiation syndrome — the animal killings are perhaps the most visceral.

"I know that was hard," writer Craig Mazin tweeted after the scene aired. "Just so there's no confusion — the story of the liquidators is real. It happened. And we actually toned it down from the full story."

Chernobyl dogs typically don't live past age six. Sergiy Romanyuk/Shutterstick

Residents forced to evacuate were told they'd eventually be allowed back in their homes. None of them were permitted to bring their pets, who reportedly chased after their owners as the buses trailed away for good. Some owners left notes begging liquidators to save their animals. Dogs that managed to escape continued to breed with one another in the wild.

More than three decades later, hundreds of their descendants roam the exclusion zone. With natural selection having run its course, the dogs are often large, sturdy breeds. There's even some evidence they began mating with wolves.

Most have Yoda-like ears that droop over at the top and their fur is often a patchwork of white, black, and brown. Few live past the age of six due to predators and harsh winter conditions.

A dog wanders through the Chernobyl Exclusion Zone. viktor95/Shutterstock

"They're very friendly, but you want to avoid petting them," said Claire Corkhill, a nuclear-waste-disposal researcher at the University of Sheffield who's been assisting with the Chernobyl cleanup.

The grown ones can carry radiation in their fur, so until 2018 it was illegal to remove them from the area.

Corkill described the dogs as "mangy" and "not very well looked after," except for by workers at the power plant who feed them scraps or adopt them as pets. Corkhill said the workers are probably petting the dogs quite often, but "they're the ones going into the reactor every day, so it's part of the risk."

Clean Futures Fund workers tag the dogs to track their radiation exposure. Sean Gallup/Getty Images

The practice of adopting Chernobyl dogs is becoming more common now thanks to the Clean Futures Fund, a humanitarian organization that supports communities affected by industrial accidents. For the past few years, the organization has been helping to spay, neuter, and vaccinate stray dogs, then release them back into the wild.

Many of the youngest dogs — those under a year old — have been determined to have safe levels of radiation, and are being put up for adoption.

Last year, the Clean Futures Fund flew more than a dozen puppies to New York City, where they were handed over to their adopted families. The puppies represent the first animals to ever be allowed outside the exclusion zone. The organization is now working to make more puppies available in the future.

Read more Chernobyl coverage:

Real-life characters in HBO's 'Chernobyl' on the moment they found out about the disaster

What HBO's 'Chernobyl' gets right (and wrong) about the world's worst nuclear power plant accident

HBO's 'Chernobyl' series invented a main character

Russia still has 10 Chernobyl-style reactors that scientists say aren't necessarily safe