Briefly

Delphi Corp., the world’s largest automotive supplier, is among six big companies said to be under examination by federal regulators to determine whether they manipulated earnings by using inaccurate estimates to calculate pension costs.

Delphi, based in Troy, Mich., disclosed Monday in a regulatory filing that Securities and Exchange Commission staff had requested documents from the company on its accounting related to pensions and retiree health benefits.

The SEC has begun such an inquiry into six companies, focusing on the assumptions they used to calculate pension costs, which can affect the bottom line, BusinessWeek magazine reported last week.

The companies were not named.

SEC spokesmen declined to comment Monday.