They are slimy pulsating sacs clinging to crevices of a sewer. As light shines on the mysterious creature, it recoils in displeasure.

Is it a new life form, or simply clever special effects?

The identity of this fearsome sewer monster has captivated the blogosphere after footage was posted on YouTube. Some even say it could be of extraterrestrial origin.


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While many experts have questioned the legitimacy of the film, a large construction firm in North Carolina has since confessed to taking the video.

Yes, those pulsating sacs are real, Malphrus Construction told MailOnline.

'We were asked by our client to inspect the sewer lines, which were built in 1949,' a spokeswoman said.

'Because the sewers are so old there were many infrastructure issues.'

But she said the moving sacs appeared much larger on camera.

Malphrus was contracted by York Properties, the owner of the sewer lines, to do a routine inspection of the pipes earlier this year.

The sewer system is private, but it discharges into the public water system, in the U.S. town of Raleigh on the east coast.

Ed Buchan, environmental coordinator at the Raleigh Public Utilities Department, was able to offer an explanation.

He said staff biologists had confirmed that the 'creature' was actually a colony of worms.

The colonies attach themselves to roots that gradually work themselves into weak points in the pipes.

'They seem to respond to the light from the camera,' he said. 'That light is pretty hot.'

He said the phenomena had been seen before, but it was very rare.

While Mr Buchan could not say what species of worms they are, other experts claim they are clumps of annelid worms, which normally live in soil and sediment at the bottom and edges of polluted streams.

The video shows that the worms have entered a pipeline somewhere and in the absence of soil they are coiling around each other.

Now the biggest mystery is how the video ended up on YouTube. Malphrus Construction has no idea, and neither does the City of Raleigh.

The video has since been removed by its owner, regular YouTube user elyhim.

But reaction to the sewer creatures was similar to the Montauk Monster incident last year, when a strange hairless, leathery body with sharp teeth, washed up on a New York beach.

A photo of the animal appeared on gossip website Gawker under the headline 'Dead Monster Washes Ashore in Montauk', and the story was picked up by media networks across the world.