Natural-gas prices climbed on Thursday after new data raised some concerns about producers' ability to meet future demand.
Gas for May delivery rose 6.9 cents, or 1.5%, to settle at $4.655 a million British thermal units on the New York Mercantile Exchange.
Trading was volatile—after falling early in the day, prices soared as much as 4% following the release of U.S. inventory data.
Last week, more gas flowed into storage than was taken out for the first time this year. Analysts had expected the increase would be 14 billion cubic feet; instead, stockpiles grew by 4 billion cubic feet, the U.S. Energy Information Administration said in its weekly storage report.
"This is very disconcerting. It's a slow start," said Teri Viswanath, natural-gas strategist at BNP Paribas.
"The industry is going to have to work that much harder to ensure" there is enough gas in storage before the start of next winter, she said.
The U.S. consumed a record amount of natural gas last winter, as freezing temperatures spurred demand for gas-fired heating.
About half of U.S. households rely on natural gas to heat their homes, according to the EIA.