Stocks are slumping at midday after the European Central Bank failed to put forward concrete new plans for calming the continent's debt crisis.

Both the Dow Jones industrial average and the Standard & Poor's 500 indexes are down more than 1 percent.

The Dow is down 144 points to 12,827. The S&P 500 is down 16 to 1,359. A third key index, the Nasdaq composite, is down 19 to 2,901.

Stocks are also down in Europe, including a 5 percent drop in Spain's main index. Spain's borrowing costs climbed above 7 percent, raising concerns that it won't be able to pay its bills.

Shares of Knight Capital Group, the trading firm blamed for a technical glitch that interrupted trades on Wednesday, plunged 50 percent to $3.48.