Natural gas and electricity provider NiSource ( NI - Get Report) said its first-quarter earnings fell 16.2% from the year-ago period, hurt by warmer weather that led to a decline in demand for natural gas in winter and higher gas prices as well. The Merrillville, Ind.-based company said Wednesday it earned $172.9 million, or 63 cents a share, in the quarter, compared with $206.3 million, or 76 cents a share, a year ago. Income from continuing operations, which excludes certain items, was $203.6 million, or 75 cents a share. On that basis, analysts surveyed by Thomson First Call were expecting earnings of $206 million, or 71 cents a share. First-quarter revenue rose 10.8% from the year-ago period to $3 billion, higher than analysts' expectation of $2.6 billion. The company expects income from continuing operations of $1.33 a share to $1.43 a share in the full year, while analysts expect $1.47 a share. "Like every company in the North American gas utility industry, we've had to deal with unprecedented weather and high gas prices that, among other dislocations, have continued to weaken residential customers' usage of natural gas and make for a more challenging regulatory-political environment," the company said. First-quarter operating income fell 15.8% from a year-ago period to $368.5 million and operating margin declined 392 basis points to 12.4%. The company's book value of common shares declined 3 cents to $18.06 a share in the first quarter compared with $18.09 a year ago. The company's stock closed Wednesday up 10 cents, or 0.5%, at $21.20.