Nicor Shares Plunge on Venture’s Problems

Shares of Nicor Inc. plummeted after the Illinois utility owner disclosed losses and accounting irregularities at an energy-marketing venture with Dynegy Inc.

Nicor, the holding company for Northern Illinois Gas, fell $15.26, or 40%, to $22.75 in trading on the NYSE. Shares of Houston-based Dynegy tumbled nearly 12% to $3.97, also on the NYSE.

Irregularities at Nicor Energy stemmed mostly from differences between estimates of natural gas sales and actual revenue, a spokesman said.