WASHINGTON — The Securities and Exchange Commission is examining major Wall Street banks to determine their vulnerability to home-loan defaults, a person familiar with the accounting inquiry said.

The person, who declined to be identified by name because the inquiry has not been publicly disclosed, described the examination as "Street-wide" and a routine part of the SEC's oversight authority.

The inquiry was reported yesterday by The Wall Street Journal, which said Goldman Sachs Group Inc. and Merrill Lynch & Co are among the first companies to be examined.

On Thursday, French bank BNP Paribas suspended three securities funds valued at $2.75 billion, saying it could not value them accurately because of problems in the U.S. mortgage market.

SEC Chairman Christopher Cox disclosed in late June that the SEC had started about a dozen investigations related to complex aggregations of mortgage debt known as collateralized debt obligations, which investors around the world purchased in recent years.

John Nester, an SEC spokesman, declined to confirm or deny the SEC's activity, other than to say that placing a value on mortgage securities "is always a concern."

The investments trade infrequently and are difficult to price and difficult for many investors to understand, experts say, leading to uncertainty that has sent financial markets into tumult this week.

"Valuations are something that our inspection teams are absolutely focusing on when they do inspections," Nester said.

SEC officials also have been examining the collapse of two Bear Stearns Cos. hedge funds that folded after making bad bets on the market for borrowers with weak, or subprime, credit.

The stock market has dived this week amid signs that credit is drying up in the mortgage and corporate buyout markets after several years in which lending standards were loosened — too far, in retrospect, many experts say. Stock markets plunged worldwide yesterday with turmoil from the U.S. mortgage crisis rippling across the globe.