U.S. derivatives regulators are examining a handful of unusual oil futures trades that took place minutes before a surprise announcement by President Donald Trump signaling a pause in attacks on Iran, according to Bloomberg News.

The investigation is being spearheaded by the Commodity Futures Trading Commission, which is scrutinizing activity on trading venues run by CME Group and Intercontinental Exchange, Bloomberg reported, citing people familiar with the matter. Both exchanges have been asked to turn over pertinent records.

Regulators are zeroing in on at least two instances over a roughly two-week period when trading volumes jumped sharply just ahead of key announcements. The information sought includes so-called Tag 50 identifiers, which can be used to determine who was behind the trades, the people said.

The CFTC declined to comment. ICE and CME didn’t immediately respond to a CNBC request for comments.

CNBC previously reported on the suspicious activity on March 23 when S&P 500 e-mini futures and West Texas Intermediate May crude futures saw a sudden and isolated surge in volume in otherwise muted premarket trading.

About 15 minutes later, Trump said on Truth Social that the U.S. and Iran had held talks and that he was halting planned strikes on Iranian power plants and energy infrastructure. The announcement triggered an immediate reaction across markets, with S&P 500 futures jumping more than 2.5% ahead of the open, and WTI crude oil futures tumbling nearly 6%.

The sudden, simultaneous spikes in volume in stock-index and crude futures raised eyebrows among traders, particularly as they came without any clear news or trigger at the time.

Last week, Sens. Elizabeth Warren, D-Mass., and Sheldon Whitehouse, D-R.I., called on the CFTC to open investigations into such unusual trades, raising the question of whether there has been recurring misappropriation of material nonpublic government information.

— Click here to read the original Bloomberg News story.