Red diesel which leaked from a sunken pontoon at Bermondsey's Cherry Garden Pier has spread upstream along the SE1 riverside and beyond, with patches spotted as far away as Wandsworth.
A barge carrying 50 tonnes of fuel sank at Cherry Garden Pier in the early hours of Tuesday morning, taking two tug boats with it.
The Port of London Authority (PLA) said one tank did not leak and a lot of oil from the other was safely pumped away.
It is thought that of the 50 tonnes of fuel carried by the barge, less than 10 leaked out. Experts believe that although it may be visible on the surface as a sheen, the diesel is likely to cause minimal damage to wildlife and will evaporate quickly.
The refuelling facility is owned by City Cruises.
"It is good news that the sunken Bermondsey pontoon and diesel leak at Cherry Gardens has apparently caused so little damage and been so well dealt with so far," commented local MP Simon Hughes.
"Of course we all need the answers as to why the pontoon sank. Of course, we all need to see if lessons can be learned to reduce such risks in the future. It is good news that there was no injury to people, and the public services responded so well.
"Bermondsey is proud of its riverside tradition, which means working boats and the ability to load, unload and fuel them along our part of the Thames. A working river means jobs, employment and prosperity for our communities. Everything must be done to make sure that we have an ever cleaner Thames and an ever better river Thames environment, but never lose the chance for people to train and work on and alongside London's most historic transport route."
A Harbourmaster's inquiry is underway.