New York ? Mixed earnings from General Electric and speculation that IBM might be under federal investigation gave Wall Street its worst day in about six weeks Thursday, as already reluctant investors decided to sell rather than risk further losses.

The Dow Jones industrials dropped more than 200 points to their lowest close since Feb. 28, while the Nasdaq composite index ended just above its Feb. 22 finish. The declines were especially striking since they came a day after a broad rally spurred by an encouraging retail report from Sears, Roebuck. Analysts said that until there is solid proof that business is recovering, the market’s mood will likely shift daily with a bias toward the negative.

The Dow closed down 205.65, or nearly 2.0 percent, at 10,176.08, giving back a big 173-point gain from Wednesday. It last finished lower on Feb. 28, at 10,106.13.

GE slid $3.45, or 9.3 percent, to $33.75 on first-quarter results that met earnings expectations but fell short of revenue projections. The conglomerate’s performance is closely watched because GE has so many different types of businesses, ranging from financial services to manufacturing and industrial operations.

Investors also had second thoughts about the technology sector. IBM fell $4.82, or nearly 5.4 percent, to $84.19 after SEC Insight, a newsletter, said the computer maker was the subject of a federal Securities and Exchange Commission inquiry. A spokeswoman said IBM does not comment on its relationship with government regulators. After the market closed, the SEC said it had opened and closed an inquiry without action concerning IBM but did not offer any specifics. IBM rebounded $3.71 to $87.90 in late trading.

The market’s regular-session losses compounded a decline earlier this week when the bellwether had warned of lower-than-expected revenues.

“People want to be able to count on stocks like GE and IBM, not worry about them,” said John Lynch, chief market analyst at Evergreen Investments.