A Thames Water spokesman says the water is not sewage.
They say it is the result of a burst water main, which had mixed with silt and mud.
Engineers are on site working to manage the problem.
A burst water main has caused flooding in south London, closing a major road. Reports suggested sewage was pouring into people's homes as a result
Local resident, Angela Reynolds, 58, said: "The road has been made into a river. It's a bit like Somerset.The water is revolting, brown, muddy - well I hope it's mud.
The water just flooded the road in 10 minutes. It was quite incredible."
A major London road was closed by the emergency services after homes were flooded with sewage as a result of a burst main.
There were reports that residents were being evacuated from their homes on Clapham Road, Kennington in South London after being trapped by the filthy water.
A policeman at the scene told onlookers "It's sewage. It's stinky. It's gone into people's basements
A Metropolitan Police spokesman said: "There is flooding on Clapham Road between Oval and Stockwell stations, which has been caused by a suspected burst water pipe.
"We are asking people to avoid the area."
Neither the fire service or police force could confirm or deny whether it was sewage causing the problem.