Raw sewage is spewing into a busy road, residents are reporting.
County Clean Environmental Services tankers are pumping out sewage from Windmill Road, at the junction with Commonside East, Mitcham.
Richard Long, a Commonside East resident who first noticed the trucks on Saturday morning, said: "At the junction there's a big puddle of raw sewage and buses and cars are going through it, not really knowing what it is."
Mr Long said the pumps are on 24/7 and had already pumped out 4,000 gallons of sewage when he spoke to a trucker before 9am on Sunday morning.
The trucks are pumping outside a recently-built block of flats, The Meadows, in Commonside East.
Chris Nawby, 61, a Commonside East resident, said: "It's disgusting. They are taking so long to do the work they are doing.
"We have got raw sewage all over the road and the noise - the people next to it must be going mad.
"We can hear the pump going all night. I'm not sure why they have taken all this time."
A Thames Water spokeswoman said: "Our teams are investigating a possible blockage in a sewer pipe and while these investigations are ongoing we're using tankers to take away wastewater from the pipe to prevent properties from sewer flooding.
"We're sorry to anyone affected by the tankering and we'll be working as fast as possible to survey the sewer and get it fixed."
Have you been affected? Contact reporter Louisa Clarence-Smith on 0208 722 6335 or email: firstname.lastname@example.org.
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