The US Commodity Futures Trading Commission is probing suspicious oil trading activity around the US war in Iran and scrutinizing prediction market trading around elections, the agency's enforcement director said on Thursday at a conference in New York.

CFTC Enforcement Director David Miller made the remarks in response to a Bloomberg News story last week that said a CFTC political appointee had told market surveillance staff to retract a referral to the agency's enforcement team identifying suspicious trading around President Donald Trump's March decision to back away from strikes on Iran's power plants.

When asked about the story during a panel at the conference, Miller said the agency had "from the beginning" been probing the trading and that the investigation remained open.

The report fueled concerns raised by investor advocates and lawmakers over a decline in enforcement activity at the agency, which is dealing with an exodus of staff as it tries to oversee the growing prediction markets industry. Prediction markets allow people to bet on the outcome of various events, from US elections to sports games.

Federal lawmakers are starting to scrutinize the industry, and most Americans oppose the idea of betting on government actions or elections, according to a mid-October Reuters/Ipsos opinion poll.

Miller also said the CFTC is watching for problematic trading in prediction markets, including on election outcomes. He declined to comment specifically on the November US midterm elections.

CFTC staff "have investigated, and may have open investigations about some candidates who have placed trades on contracts that are based on their own elections," Miller said.