The size exceeds previously reported bets amounting to $2.6 billion, which have already prompted the US administration to warn staff against using nonpublic information for financial benefit.

The US Commodity Futures Trading Commission (CFTC) is investigating, a person familiar with the matter told Reuters in April, although the CFTC has yet to officially confirm a probe is underway.

Reuters could not establish who placed the bets and whether they originated in the US or elsewhere. They included short positions, or bets that prices would fall, for derivatives including ICE, CME crude, diesel and gasoline futures.

The bets took place on two major exchanges that host benchmark global oil and fuel futures trade: the Intercontinental Exchange (ICE) and Chicago Mercantile Exchange (CME). Both exchanges declined to comment. The CME is investigating the trades, a source familiar with the matter told Reuters.

The well-timed trades have triggered calls from legal experts and lawmakers for regulators to investigate whether they were based on inside information or leaks.

Traders first spotted unusual trades on March 23. The trades were executed minutes before Trump announced a delay to threatened attacks on Iranian power infrastructure, triggering an oil price fall.

The same pattern repeated on April 7, before Trump announced a ceasefire with Iran that triggered a fall of as much as 15% in benchmark ICE Brent futures.

It happened again on April 17, when Iranian officials and Trump spoke about reopening the Strait of Hormuz, and then again on April 21, when Trump extended the ceasefire.

Reuters and other media reported those trades on the most actively traded front-month contracts for the two global crude benchmarks, Brent and West Texas Intermediate.

 The value of those bets on those four days in March and April stood at around $2.6 billion, according to Reuters initial calculations.

The US Justice Department, CFTC and White House did not immediately respond to requests for comment.

However, a further analysis of trading data across exchanges and contracts showed traders executed similar bets at exactly the same dates and times for European diesel and US gasoline futures as well as longer-dated contracts for Brent and WTI, bringing the total to around $7 billion, based on Reuters calculations.

A sell bet – or short selling – means the person executing the trade borrows the derivative from a counterparty, sells it and later buys it back more cheaply when the price falls, keeping the remaining cash as profit.

On March 23 and on April 7, 17 and 21, oil prices plunged by over 10%. Reuters calculations show that a short seller with $7 billion could have made hundreds of millions of dollars in profits, depending on the timing of the bets.

The trades look “well informed” as they preceded major announcements, said Adi Imsirovic, from the Center for Strategic and International Studies (CSIS), and a veteran oil trader. US authorities, such as the CFTC, can access exchange data to trace who placed the trades and investigate if it decides to, he added.

On Thursday, ABC reported the US Department of Justice was investigating $2.6 billion in oil trades related to the Iran war. The DOJ was not immediately available for comment.

The CFTC’s enforcement director said in March the agency was aware of speculation regarding insider trading in CFTC-regulated markets and was “watching”.