When a video of a mysterious, slimy "creature" living in the sewers of Raleigh, N.C., was posted on YouTube early this week, millions around the world flocked to the site to satisfy their curiosity.
Since June 30, "Unknown Lifeform in North Carolina Sewer!" has been viewed more than 4.7 million times.
Some called it an extraterrestrial, others believed it was monster, much like the "Montauk Monster" purported to have washed up on a Long Island, N.Y., beach.
The video, posted by someone apparently with the Web site UFORadar.com, shows a shiny, slimy mass pulsating for the camera.
But it appears that the bizarre mystery has been solved.
Local officials told news outlet News 14 Carolina that the "creature" is nothing more than a colony of tubifex worms.
Ed Buchan, environmental coordinator at the Raleigh Public Utilities Department, told the news outlet that staff biologists had confirmed that the oddity was a colony of worms. The colonies attach themselves to roots that slowly work their way into weak points in the pipes.
Their movement, he suggested, was a response to the heat from the camera's light.
"They seem to respond to the light from the camera," Buchan said. "That light is pretty hot."
He said the worms live in sewage and pond sediment, but he hadn't seen them in the sewer before.
"We were surprised. We didn't know immediately what it was," he said.
But he added that the worm colonies, bizarre though they may appear, don't pose problems for the city's water quality.
"You want to try to keep the pipe as clear as possible regardless of what's in there," Buchan said. "On the other hand, it doesn't seem to be causing any blockage."
But a biology professor with the North Carolina State University told News14 it might not be a colony of worms but something else.
"I think it's a colony of bryozoans," Kwak said. "They are small animals like a hydra that live together in colonies, and they stick out tentacles to feed. And when they're disturbed, they withdraw into small tubes that they've built."
But he also said there's no reason to clear them out unless they begin to clog the sewer pipe.
Although some doubted the legitimacy of the video, the U.K.'s Daily Mail confirmed with Hilton Head Island, S.C.-based Malphrus Construction that the video is indeed real.
"We were asked by our client to inspect the sewer lines, which were built in 1949," a spokeswoman told The Daily Mail. "Because the sewers are so old, there were many infrastructure issues."
But she said that the colonies look much larger on camera than they actually are.