TANKERLOADS of drinking water have been shipped to the eastern Montana city of Glendive after traces of a major oil spill along the Yellowstone River were detected in public water supplies.

Preliminary tests at the city’s water treatment plant indicated that oil got into a water supply intake along the river. 

Officials claimed that Monday’s shipments of drinking water were merely a precaution and they did not know yet whether there was any health threat. 

Results of further tests were expected in coming days.

Up to 50,000 gallons of oil spilled in the pipeline accident on Saturday. Clean-up crews trying to recover the spilled crude were hampered by ice that covered most of the river, making the oil hard to find.

Initial tests of water supplies over the weekend revealed no evidence of oil. But by late Sunday residents were complaining that the water coming from their taps had an unusual odour.

Company spokesman Bill Salvin said that the firm was confident that no more than 1,200 barrels of oil spilled during the hour-long breach.

An oil sheen was seen almost 60 river miles downstream from Glendive, said the co-ordinator for the US Environmental Protection Agency.

Booms were being placed in areas of open water to try to trap oil and about 30 miles downstream from the spill and crews were chopping holes into the ice in the hope that they would be able to vacuum up the crude as it drifts downriver in the coming days.