The U.S. is investigating whether traders with inside information on Russia’s negotiations with other oil producing nations made hundreds of millions of dollars from illegal wagers on crude price swings, according to two people with direct knowledge of the matter.

The Commodity Futures Trading Commission probe is focused on whether aspects of the strategy that the Russian government pursued last month with other members of the OPEC+ coalition leaked out to market participants ahead of time, said the people who asked not to be named because the scrutiny isn’t public. For the same reason, the U.K.’s Financial Conduct Authority is also investigating suspicious trades in futures contracts, one of the people said.

The inquires predate the Monday spasms in oil markets that pushed U.S. prices into unprecedented negative territory.

While the names of the traders involved couldn’t be identified, they aren’t Russian government officials, the people said. Still, the entities that made the bets do employ individuals with ties to the Kremlin, according to one of the people. The subjects of the investigations aren’t Americans, another person said. The CFTC is mainly scrutinizing transactions involving CME Group Inc. West Texas Intermediate contracts that expired before Monday’s price swoon.

Spokesmen for the CFTC and FCA declined to comment. Kremlin spokesman Dmitry Peskov also declined to comment.

Oil markets have seen a precipitous decline since March, as the coronavirus pandemic eroded demand and Russia and Saudi Arabia engaged in a price war. Concern that traders obtained non-public information on Russia’s stance during that standoff is at the center of regulators’ investigations, the people said. The individuals being scrutinized had no history trading futures, the people said.

The CFTC is being assisted in its investigation by other agencies, including the Federal Bureau of Investigation and State Department, one of the people said.

Concern that futures traders might be benefiting from insider tips prompted lawmakers to include a provision in the 2010 Dodd-Frank Act that made it illegal to profit from leaked government information. Recently, the CFTC has made an effort to prioritize insider trading, announcing in 2018 that the agency had formed a specialized task force to pursue such misconduct.