The acknowledgments by the nation's two largest automakers came a day after Delphi Corp., the world's largest automotive supplier, disclosed in a regulatory filing that the SEC had requested documents on its accounting related to pensions and retiree health benefits, which can affect the bottom line.

Confirming a report in BusinessWeek magazine, the SEC said its inquiry started with six companies it did not name. The SEC has no evidence of violations, but the companies were not selected randomly, said Lawrence West, an associate director of enforcement at the agency.

GM spokeswoman Toni Simonetti said Tuesday the automaker received a confidential request from the SEC last Thursday to provide information about its pension and post-retirement health care plans. Simonetti said the company was complying with the request.

"We're confident GM's financial reporting in this complex area has been accurate and complete," she said.

Ford chief financial officer Don Leclair acknowledged receipt of the SEC request Tuesday during a conference call with analysts and automotive journalists to discuss Ford's third-quarter earnings.

"Given the size of our pension and retiree health care obligations, I don't think it's surprising that a general SEC inquiry on these matters would include Ford," Leclair said. "We adhere to the highest accounting standards and will cooperate with the agency in this review."

Company pension plans are among several areas being examined in the SEC's new "risk-based inquiries" designed to anticipate problems that could lead to fraud and investor losses. Critics have suggested in recent years that some companies are using artificially high estimates of future rates of return on pension assets to lower their pension costs, thereby pumping up earnings.

The SEC is examining whether changes in pension plans can create so-called "cookie jar" reserves that could be dipped into to bolster revenues in less profitable times. The SEC maintains such a practice gives investors an inaccurate picture of a company's financial performance.

The regulators also are looking at the discount rate, based on corporate bonds, used to calculate future pension liabilities. A change of one-half percentage point can affect large pension plans by hundreds of millions of dollars.

In a similar initiative, the SEC is investigating reporting of circulation figures in the newspaper industry following several disclosures of fraudulent practices in recent months.

In afternoon trading on the New York Stock Exchange, GM shares were down 54 cents at $38.37. Ford shares were down 19 cents to $13.20.

-- John Porretto