Fifers were left wondering what caused two burns to turn an irn-bru shade of orange, last month.
Scottish Environment Protection Agency (SEPA) officers investigated the pollution incident, took samples, and carried out analysis at their laboratories in North Lanarkshire.
Both Claremont Burn and Kinness Burn were turned bright orange when mine water containing naturally occurring iron was released following heavy rain.
The investigation team believe the contamination was a short-term issue with limited environmental impact.
Paul Butler, mining sector lead at SEPA, said: “We would like to thank members of the public for reporting the recent pollution incident in the Kinness Burn.
“The discolouration in the Claremont Burn and Kinness Burn was caused by iron and was associated with historic mine workings in the area.
“SEPA officers attended the location to investigate the cause of the pollution and undertake monitoring. There was no evidence of ongoing discolouration at the time of the visit. The event appears to have been a short-term issue with limited environmental impact.
“Water from mine workings contains naturally occurring metals, such as iron, produced from the mined rocks. When mine water flows into a river, the iron causes the water to change colour.
SEPA will continue to work in partnership with the Coal Authority to investigate any further incidents.
Members of the public concerned about potential pollution can contact SEPA using its 24-hour online form at - www.sepa.org.uk/report.