A Raleigh Public Works engineer told TheDenverChannel the video is easily explained.
"They're a colony of tubifex worms," said Senior Project Engineer Mark Senior. "We've seen them before in sewer systems."
Senior said the video was shot "a couple of months ago" by a private contractor -- Malphrus Construction -- inspecting a private 6-inch sewer line that flushes into the city sewer system.
Since the video was posted on YouTube, and reposted around the world, his office has been fielding dozens of phone calls and e-mails.
The video is misleading, Senior said, because it was taken in a 6-inch sewer line.
"The objects are only about 1/2 inch across," he said, "They look bigger in the video."
The worms' reaction to the camera is thought to be a result of heat from the camera light.
Tubifex worms are also called sludge worms, sewage worms, or lime snakes.
"(Tubifex worms) are normally found in the sediment of ponds and are sold as fish food in both live and dried forms," said Ed Buchan, environmental coordinator for the City of Raleigh. "The worms are completely harmless. Because of frequent cleaning and maintenance efforts, the worms are rarely found in city sewer lines."
It wasn't clear how the video from the private contractor ended up on YouTube.
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