Federal disclosure forms released have shown President-elect Donald Trump holds stock in the firm building the Dakota Access oil pipeline.
Trump is said to own between $15,000 and $50,000 in stock, down from between $500,000 and $1million the year previously.
Trump also owns between $100,000 and $250,000 in Phillips 66.
Earlier this month, the Obama administration said it wants more study and tribal input before deciding whether to allow the partially built pipeline to cross under a Missouri River reservoir in North Dakota.
The 1,200-mile pipeline would carry oil across four states to a shipping point in Illinois.