Trump's 2016 federal disclosure forms, filed in May, show he owned between $15,000 and $50,000 in stock in Texas-based Energy Transfer Partners.
That's down from between $500,000 and $1 million a year earlier.
Trump's form also shows he holds between $100,000 and $250,000 in Phillips 66 stock, which has a one-quarter share of Dakota Access.
Campaign contribution disclosures show that Energy Transfer Partners CEO Kelcy Warren donated $3,000 to Trump's campaign, plus $100,000 to a committee supporting Trump's candidacy, as well as $66,800 to the Republican National Committee.
Trump's stake and the donations were first reported Wednesday by The Guardian.
Copyright 2016 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.