Teco Energy Inc., owner of the power utility in Tampa, Florida, said it’s considering a potential sale as the industry faces increasing costs to meet new environmental rules. The shares rose the most in more than six years.

The company has retained Morgan Stanley to explore strategic alternatives, it said in a statement Thursday. News of the sale was reported earlier by SparkSpread. The shares closed 16 percent higher at $21.48 in New York, the biggest one-day gain since October 2008.

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