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Thames Water has raised an alert after ammonia leaks were possibly fly-tipped into the Banbury sewage system, affecting the River Cherwell.

A rivers improvement organisation, Thames 21, has appealed to the Banbury area community to help the search for the cause so it can be halted and, if appropriate, the fly-tipping perpetrators found.

A Thames Water spokesperson said today (Tuesday): "On Saturday, May 11, we observed high levels of ammonia leaving our Banbury sewage treatment works.

"Our teams investigated straight away and suspect a harmful substance may have been fly-tipped into the sewer system.

Banbury Sewage Treatment work which has been compromised by an ammonia leak - possibly caused by fly-tipping

"This substance has impacted the biological process, which helps us to treat ammonia arriving at our sewage treatment works. We are working closely with the Environment Agency on our investigations to identify the potential perpetrators.

"Over the weekend, members of the public may have noticed odours coming from the site or within Banbury, if anyone has any information relating to this we would encourage them to get in contact with us.

"We've begun work to regrow the bacteria needed for the process by taking flows from other sites and expect to see improvements over the coming days. During this time customers may see increased tankering activity around the site as we aim to try and manage the impact to the environment. We apologise for any inconvenience this may cause."

Claire Robertson of Thames21 posted on Banbury social media to ask for help from the public in a bid to prevent more pollution of the river Cherwell.

A Thames Water email alerting officials to the ammonia leak incident

"Essentially high levels of ammonia have knocked out treatment processes, meaning more pollution going into the river,” she said.

She has asked residents or visitors to the area to let her know if they noticed a horrible smell between Friday and Sunday; when it started or stopped and the rough location of where they smelt it. She asked them to email her at [email protected] or to report directly to the Environment Agency on 0800 80 70 60.

Thames 21 works with communities to improve rivers and canals for people and wildlife, mobilising thousands of volunteers every year to clean and green London and the Thames’s 400 mile network of waterways.

Water company raises alert after 'fly-tipped' ammonia leaks into Banbury sewage system, polluting river