United States Natural Gas Fund LP (UNG) will resume issuing new shares starting Sept. 28, the fund said in a filing with the Securities and Exchange Commission.

On Aug. 12, the fund said it would stop issuing shares, citing fears that the Commodity Futures Trading Commission would set new position limits on energy trading. Since then, the fund has engaged in over-the-counter transactions known as swaps to bring the exchange position under any potential limits.

UNG and other exchange-traded funds, or ETFs, sell shares on stock exchanges, then use the investment to buy futures contracts. Commodity ETFs have grown enormously over the last three years, with UNG seeing particularly rapid growth in 2009. The fund saw $4.6 billion in net inflows through August, according to the National Stock Exchange.

Regulators and lawmakers in Congress have said they are concerned that ETFs that solely take positions betting that commodity futures will rise, including UNG, have artificially inflated prices.

Other ETFs and similar products known as exchange-traded notes have also suspended issuances, including Barclays PLC's (BCS) iPath Dow Jones-UBS Natural Gas Subindex Total Return ETN (GAZ). In August, Deutsche Bank AG (DB) said it would close its PowerShares DB Crude Oil Double Long (DXO) ETN.

UNG shares are trading at a 15% premium to the value of the underlying natural gas contracts, as investor interest in the fund has remained strong since the share issuances stopped. That premium is now in jeopardy.

"It is possible that the resumption of creation activity, even on a limited basis, could reduce or remove any premium," the fund said in the filing. "Investors are cautioned that paying a premium...for UNG units can lead to additional losses for the investor in the event that the investor sells such units at a time when the premium is no longer present in the market price."

-By Brian Baskin, Dow Jones Newswires; 212-416-2453; brian.baskin@dowjones.com