Updated from 3:35 p.m. ESTThe major indices steep losses continued into the final hour of trading Thursday, erasing a modest midweek rally, amid concern for automaker General Motors ( GM), caution on U.S. banks, and mixed economic news. The Dow Jones Industrial Average fell 280.52 points, or 4.08%, to 6595.32, and the S&P 500 gave up 30.31 points, or 4.3%, to 682.56. The Nasdaq declined 54.15 points, or 4%, to 1299.59, below its November 20 closing low of 1,316.12, and just above its November 21 intraday low of 1,295.48. Alcoa ( AA), down 16%, and General Motors, down 17%, led the decliners on the Dow. The struggling U.S. automaker said in a 10-K filing that auditors have raised "substantial doubt" about its ability to continue as a going concern. Financials took their own beating after Moody's Investors Service said it might downgrade its ratings of Wells Fargo ( WFC) and Bank of America ( BAC) out of caution for potential loan losses. The ratings company expressed concern about JPMorgan as well. Bank of America, Citigroup ( C) and JPMorgan ( JPM) were all more than 10% lower, with Citi at times dipping below $1 a share. "It's too soon to talk about how we'll turn around, people are talking about how to protect themselves in this environment," says Michael Pento, chief economist for Delta Global Advisors. "I don't think market is at all enthused with the various stimulus packages that are out there -- or with the amount of debt that we're loading on future generations," says Pento. "It wants long-term, strong solutions for the economy, country, and currency." Chinese Premier Wen Jiabao did not unveil new stimulus on Thursday, despite previous market-moving reports that he would, but other efforts to deal with the economic downturn overseas were announced. Namely, the European Central Bank slashed its main interest rate by a half percentage point to 1.5%, a new record low.