US state North Dakota confirmed on Thursday that it had discovered a new radioactive waste dump from oil drilling.

Separately a Canadian company hired to clean up waste found in February at another location said it had removed double the amount of radioactive material originally estimated.

The company also said it suspects the soil at the site is contaminated.

The twin disclosures highlighted a growing problem from North Dakota’s booming oil development — illegal disposal of oil filter socks, tubular nets that strain liquids during oil production and contain radioactive material. 

Radioactive filter socks are increasingly found at roadsides, in abandoned buildings or in commercial rubbish bins.

State environmental health chief Dave Glatt said investigators are examining the new site north of Crosby which was discovered late last week. 

State health department waste manager Scott Radig claimed there was little danger to the public from the radioactive waste “except from ingestion or inhalation.”