The source of an oil leak in a central Christchurch river has likely been found, Canterbury Regional Council says.
The council was alerted to oil leaking into Ōtākaro / Avon River from a stormwater drain near the Antigua Boatsheds on 29 April.
A short time later, booms and a pump were installed to contain the spill, a council spokesperson said.
They estimated between 200 and 300 litres may have been discharged into the river.
But the situation had since improved.
"Only trace residue appears to be discharging into the river, which we are continuing to monitor and remove," the spokesperson said.
"There is no evidence at this stage of large quantities still emerging from the pipe."
Council staff thought they had identified the source but were unable to comment further while it was being investigated.
Staff worked with Christchurch City Council to check higher-risk sites and check stormwater in and around the networks.
They had also gone door to door in the nearby area looking for any high-risk activities which may have led to a spill and published targeted advertisements on Facebook.