The spillage happened after four ruptures appeared in the pipeline that runs from its tailings processing plant to under water storage pits located at Bige.
OTM said in a statement it took immediate steps to shut down the pipeline, however, this did not prevent some of the pyrite concentrate that was still in the pipeline from leaking into the environment.
Pyrite can be potentially harmful to the environment because it can produce acid during exposure to air and water.
It is estimated that between 100 and 200 cubic metres of pyrite concentrate was lost through the ruptures.
To date monitoring of the impacted streams has shown no evidence of acidification and OTM has reassured monitoring would be ongoing during and after the spillage clean up.
Creeks and streams near the Ok Tedi mine have been affected by the spill and while officers from OTM's Environment and Community Relations Departments are working to improve the affected areas, it may take up to several weeks to complete the clean up.
Current results from the sampling and monitoring program indicate pyrite is visible in streams up to 2 kilometres downstream of the ruptures.
Despite this the company has reassured local communities that the water is safe to use.
OTM managing director Nigel Parker said everything was being done to ensure the communities were not affected by the spill and the company would be communicating to communities the results of the environmental assays for water quality.
The Ok Tedi mine remains suspended, however, OTM has been in discussions with impacted communities and the state on its plans to recommence production while the pipeline is being repaired.