NEW YORK — New weekly statistics from the Federal Reserve show that investors for a fourth straight week kept away from the corporate commercial paper market, which in good times is a reliable source of short-term funds for companies.

During the week ended Wednesday, the outstanding volume of commercial paper dropped by $54 billion, or almost 3 percent, to $1.93 trillion, after many companies couldn't find takers for these notes. The decline follows a massive outstanding paper decline of $259 billion, or almost 12 percent, in August.

Asset-backed paper, such as notes backed by mortgages and credit cards, fell by $31.3 billion, or more than 3 percent, to $966.7 billion in the latest week.

The commercial paper market, normally highly liquid, last month began receiving intense resistance as worries about exposure to below-prime mortgages and other shaky assets took their toll on many corporate credit markets.

Negative news stories about commercial paper, which generally has a maturity of 45 days or less, helped keep this market out of favor in the most recent week.

On Wednesday Moody's Investors Service downgraded or said it might downgrade $14 billion in what are called structured investment vehicles, which are funds dependent on the commercial paper market for borrowing. These vehicles typically sell short-term commercial paper to buy longer-term bonds, sometimes including mortgage-linked debt.