Thames Water is investigating a discharge at its Wheatley Sewage Treatment Works site in south Oxfordshire.
Several tankers are now at the site helping to clean up the mess, which is said to be affecting the River Thames today (Monday, July 28).
A third party is said to have caused the discharge, according to Thames Water, and it is understood wildlife could be affected.
Wheatley councillor Tim Bearder described the discharge as “category one, the most serious” and a “chemical incident”.
Tankers clear up (Image: Tim Bearder)
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He added: “Trucks are there and the treatment plant is closed while investigation work is carried out.”
Liberal Democrat Henley and Thame MP Freddie van Mierlo said he is “extremely concerned” by reports of a “serious pollution incident” affecting the river.
“We don’t yet know the full extent, but it’s clear that something has gone badly wrong,” he said.
“I’ve asked for urgent updates from Thames Water, and I’m grateful for the swift response from local councillors and community members.
“The River Thame is a vital part of our local environment, supporting wildlife. Residents rightly expect strong protections to be in place.
“Once the facts are established, we must ensure that those responsible are held to account and that everything possible is done to restore the health of the river.”
Freddie van Mierlo (Image: Contributed)
A spokeswoman from Thames Water said: “We have identified the source of the substance as a third-party disposal into the wastewater network, which we have now stopped.
“We are carrying out a full clean of the surrounding sewers and pumping station to ensure they are clean, clear, and free flowing.
“We have deployed tankers, to divert the wastewater flows to an alternative site in order to minimise the impact to the watercourse and we are working closely with the Environment Agency and local stakeholders during this time to ensure full recovery.”
She said the company will pursue an investigation into the source of the substance and vowed “appropriate action” will be taken.
Thames Water did not confirm what was discharged into the river.
The Environment Agency has been approached for a comment.