The two major oil and natural gas-tracking exchange traded funds (ETFs) remain under the microscope this week as the CFTC resumes its investigation about their role in the commodities markets run-up and the role speculators had, if any.

On Wednesday, the chief investment officer of the popular United States Oil (USO) and the United States Natural Gas Fund (UNG) will testify at a Commodity Futures Trading Commission hearing as part of the agency’s efforts to curb speculation. Carolyn Cui for The Wall Street Journal reports that the regulators are wondering whether the commodity funds are influencing the prices of the markets they track.

John Hyland, the chief investment officer for the funds, has vigorously defended them and said he has yet to see any evidence that the ETFs are influencing prices. “Most of these claims have as much validity as claims that the attack on Pearl Harbor was the work of Sweden,” Hyland said in a statement. The hearings, he said, will “hopefully put this nonsense to rest once and for all.”

The CFTC considers a speculator to be those who invest in commodities for financial reasons and do not take physical delivery of the commodities underlying a futures contract.

Thus far, the two ETFs have grown over the past year rapidly, and account for the majority of buying taking place in their respective markets. A witness list was issued Friday.

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