Water firm bosses have said they are treating technical problems which resulted in raw sewage being dumped into the River Thames as a 'matter of urgency'.
Thames Water has apologised again after sewage spilled into the river on Sunday from Little Marlow Sewage Treatment Works.
It is the third time in three weeks river users have had to put up with the foul smelling mess.
A statement released today from Thames Water said: "We're really sorry for the mess this has caused.
"We're investigating with a matter of urgency how this happened."
It added surrounding rowing and sailing clubs who use the river were notified of the latest spillage on Sunday evening.
A back-up system has been used at the sewage treatment works since the fault was first identified but failed to prevent the latest spill.
The Environment Agency (EA) has been involved in a clean-up operation of the river and said it is continuing to investigate the problem.
An EA statement said: "We are working with Thames Water to ensure the processes on site are working properly to prevent any further pollution.
"We are confident that risks of further pollution are being managed."
It would not comment on whether legal action would be taken against Thames Water, which operates the sewage treatment works, while it was carrying out its investigation.
On Wednesday last week Thames Water confirmed there had been seven 'accidental' sewage leakages in the Thames in the last six months.
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