HOUSTON, Feb. 6 — Shares of independent power producer Calpine Corp. fell Wednesday in heavy trading after the company reported the US Securities and Exchange Commission is looking into allegations of selective disclosure of information.

The stock was down 20% to $7 on nearly 50 million shares traded, compared to average volume of 12.7 million shares. Calpine confirmed it has received an “informal request for information from the enforcement division” of the SEC regarding a newswire report, which made claims that the company may have made selective disclosures to analysts. That is now forbidden under the agency’s Fair Disclosure rule adopted last year.

In a separate and unrelated matter, Calpine said it also received a comment letter from a nonenforcement arm of the SEC seeking clarification and offering advice on “certain disclosures.” It did not specify what disclosures. Calpine said the comments will not require the company to alter “any aspect” of its financial results.

Calpine said it hasn’t made inappropriate disclosure, and that it is working with the SEC. The company said that it has had — and will continue to have — an ongoing dialogue with its accountants, lawyers, and the SEC to continually enhance its financial disclosure practices.

Calpine shares already were under pressure because electricity prices have been falling. Last week Merrill Lynch & Co. analyst Elizabeth Parella cut her 2002 earnings estimate for Calpine to $1.45/share from $1.60/share and blamed the weak outlook for natural gas and electricity prices.

“Under this scenario, CPN may have a tougher row to hoe than some others, in view of high leverage and tight cash situation,” she wrote in a research note. Gordon Howald, an analyst with Credit Lyonnaise, also expressed concern that with spark spreads at such low levels, “that as Calpine adds capacity during 2002 unit margins will come under further pressure and that full year earnings will disappoint.”

Calpine reported a 23% decline in fourth quarter 2001 earnings on weak power prices and poor prospects of a recovery until industrial demand begins to rise.