Activist investor Elliott Investment Management LP has built up a more than $2.5 billion stake in Phillips 66, and is looking for the oil company to either sell or spin off its midstream unit to help boost its stock price.

Phillips 66 shares are jumping 4% in intraday trading Tuesday following a report by The Wall Street Journal that Elliott Investment Management has built a more than $2.5 billion stake in the oil refiner.

Elliott Investment Management confirms a more than $2.5B stake in Phillips 66 and will seek to streamline the company, most notably with the sale or spinoff of its midstream business.