Wall Street fell sharply again Thursday after a French bank said it was freezing three funds that invested in U.S. subprime mortgages because it was unable to properly value their assets. The Dow Jones industrials fell more than 200 points.

The announcement by BNP Paribas raised the specter of a widening impact of U.S. credit market problems. The idea that anyone – institutions, investors, companies, individuals – can’t get money when they need it unnerved a stock market that has suffered through weeks of volatility triggered by concerns about available credit and bad subprime mortgages.

A move by the European Central Bank to provide more cash to money markets intensified Wall Street’s angst. Although the bank’s loan of more than $130 billion in overnight funds to banks at a low rate of 4 percent was intended to calm investors, Wall Street saw the step as confirmation of the credit markets’ problems. It was the ECB’s biggest injection ever.

The Federal Reserve added a larger-than-normal $24 billion in temporary reserves to the U.S. banking system.

The ECB’s injection of money into the system is an unprecedented move, said Joseph V. Battipaglia, chief investment officer at Ryan Beck & Co., adding that it offers evidence that the problems in subprime lending are, in fact, spilling into the general economy. [MORE]