(Bloomberg) -- One oil exchange-traded fund saw its largest one-day outflow in more than three years, a possible sign that some investors remain concerned about the outlook after OPEC+ delivered an unexpected supply cut.

Most Read from Bloomberg

• Saudi Arabia’s Drive to Get Expats to Ditch Dubai Is Off to a Rocky Start

• A $1.5 Trillion Wall of Debt Is Looming for US Commercial Properties

• Taking Crimea From Putin Has Become ‘Operation Unthinkable’

• Tesla New Battery Plant Cements China’s Place in Energy Storage

• Bond Market Is Overplaying the Risk of a Deep Recession

WisdomTree’s Brent Crude Oil ETP — ticker BRNT — had an outflow of $55.7 million on Thursday, the largest one-day fall since late 2019. Another fund, the ProShares Ultra Bloomberg Crude Oil ETF — ticker UCO — saw outflows of $158.5 million last week. That’s its biggest weekly drop since March 2022.

The Organization of Petroleum Exporting Countries and its allies announced a surprise output cut earlier this month, led by Saudi Arabia. While that helped prices to surge last week, concerns about a potential slowdown in demand have lingered. There’s speculation both that the US could tip into recession, hurting consumption, and OPEC+ actions telegraph its concerns about market weakness.

“There is still a large segment of the market concerned over the demand outlook and OPEC+ cuts would have likely only reinforced these concerns,” said Warren Patterson, head of commodities strategy at ING Groep NV in Singapore.

Most Read from Bloomberg Businessweek

• What to Do With Your Money—and Your Life—in a Wild New World

• Scaramucci’s SkyBridge Capital Was Spiraling, and Then Came FTX

• Apple’s Complex, Secretive Gamble to Move Beyond China

• The Chainsmokers Are Dancing Through the Silicon Valley Downturn

• AI Is Moving Fast Enough to Break Things. Sound Familiar?

©2023 Bloomberg L.P.