The Coal Authority is continuing investigations into a leak which has discoloured part of the upper Calder Valley’s river system.
Last Thursday morning residents reported discolouration in Midgelden Brook, which runs down the length of Bacup Road, Todmorden, where it joins Walsden Water which in turn meets the River Calder at Todmorden town centre.
A nearby resident said: “It looks like its contaminated - bright orange and green, and it smells.”
The incident was reported to the Environment Agency which in turn contacted the Coal Authority, which has a mine water treatment scheme nearby.
Yesterday, the issue was still being investigated, said the Coal Authority.
Tracey Davies, Head of Environment, Coal Authority, said: “On Thursday, 24 March 2016, we received a report of discolouration of the Midgelden Brook.
“We responded quickly and instructed our operational contractors to visit the site to carry out an initial assessment of the watercourse and our mine water treatment scheme nearby.
“These initial investigations indicated that the discolouration was not linked to the treatment scheme.
“We are currently undertaking further investigations to determine its cause and are continuing to work closely with the Environment Agency.
“Residents can report incidents like these directly to us on 01623 646 333, 24 hours a day, seven days a week.
“Details are available on gov.uk/coalauthority.”