Environmental bosses are continuing to investigate the pollution of a stretch of Wigan waterway after managing to solve the issue.
The Environment Agency (EA) had to work fast after thousands of fish died in the Leeds-Liverpool Canal between Haigh and Top Lock just before the new year.
The oxygen-starved water became a death trap for wildlife on Boxing Day, with white frothy substances in the canal and discolouration spotted from the Withington Lane bridge.
EA officials have now traced the source of the problem to a landowner in the Wigan area and believe the issue has been rectified.
The official probe into the alarming incident is ongoing and court action cannot be ruled out if enough evidence is gathered.
An EA spokesman said: “The Environment Agency is centring investigations at a site local to the Leeds-Liverpool canal in the Wigan area.
“The course of any legal action will be decided after the investigation is completed.”
Fisheries officers said on social media this week that they had been working to improve land management practices.
A tweet on the subject concluded: “Oxygen levels in the canal are back to normal. We aren’t expecting a recurrence.”
The same Twitter account also posted a picture of officer Darren Wilson restocking the stretch of water with 1,000 roach raised at the agency’s national fish farm.
The EA posted several dramatic videos on Twitter over several days of work on the canal just after Christmas.
Fish were seen swimming close to the surface, obviously in some distress from the hazardous conditions in the water.
Other clips showed EA employees treating the canal to restore oxygen levels, with aeration taking place over a couple of days and areas where there were still problems being dosed with hydrogen peroxide after that.
The North West Waterways initially raised the alarm over the low oxygen levels in the canal. The Canal and River Trust was also given the job of monitoring the water after it had been treated.
The sight of the treatment work caused some concern among regular visitors to the waterway.