Sydney Water has apologised after an incident that saw a large volume of untreated wastewater flow into the Parramatta River.

Wastewater flowed into the Parramatta River from a wastewater pumping station at Northmead, but the cause of the spill is still being determined.

“Our first priority was to contain the overflow and protect the waterway,” Sydney Water said in a statement.

Bypass arrangements are in place to control the flow, with additional pumps installed at the site to minimise impacts. Large tankers continue to attend the site to pump out wastewater as required.

“We apologise for any inconvenience this may cause to residents in the area,” the authority stated.

Sydney Water has signage in place around the site and along Parramatta River to the Ferry Wharf to advise the local community of the overflow.

“Sydney Water takes its responsibility to protect public health and the environment seriously, and we will conduct a full investigation of this incident to prevent it from happening again across our network.”