JACKSON, Miss. (AP) — Sempra Energy says it's opened a second natural gas storage cavern at its Mississippi Hub storage facility in Simpson County.

With approval from the Federal Energy Regulatory Commission, the San Diego-based energy firm said the 7.5 billion cubic-foot underground cavern is open for business. That doubles Sempra's storage capacity at the site southeast of Jackson, Miss., to 15 billion cubic feet.

Sempra said it plans to finish construction of a third cavern next year, boosting total capacity to 22.5 billion cubic feet.

The company didn't disclose a price for the project Thursday. Sempra spent $122 million last year on construction projects at Mississippi Hub and a similar storage facility in McIntosh, Ala.

Earlier this year, Sempra bought Willmut Gas & Oil Co., a Mississippi natural gas utility.