Dzerzhinsk, Russia - Pictures of dogs with blue fur went viral last week, raising concerns about the animals' welfare, but according to experts, the canines seem otherwise healthy.

According to the Russian news agency RIA Novosti and Newsweek, the Federal Service for Supervision of Natural Resources, which is known as Rosprirodnadzor, is currently investigating the cause of the dogs' strange coloration and trying to get permission to do spot checks of the area in which the animals were found.

The dogs with blue fur were first spotted in Dzerzhinsk on the site of the former petrochemical company Orgsteklo, which produced plexiglass and hydrocyanic acid before it went bankrupt in 2015. The authorities were able to gain access to the factory grounds and catch seven of the blue dogs.

Images of the animals went viral on the VK social networking website, and the story was picked up by local media.

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According to Newsweek, some people thought the dogs had ingested chemicals that turned them blue, while others thought their wild coloring was a prank and that the dogs had been painted.

Vladimir Groisman, the director of a veterinarian center, examined the dogs and said, "We have already performed initial analysis on the animals. The general analysis of their blood and feces showed normal levels for all of them, including their biochemistry."

Groisman thinks that the dogs got stained blue when they took shelter from the cold in the old factory. He doesn't think the animals were painted, but admitted, "We do not yet know what caused the dyeing of dogs' fur. This requires large scale analyses, which we cannot do here."

The dogs will be held for a week of observation. Two of the animals have already found new owners.