NEW YORK (MarketWatch) U.S. stocks swung between small gains and sharp losses in heavy trading Friday afternoon as the frenzied trading that rattled investors on Thursday showed few signs of abating.

In early afternoon trading, Dow Jones Industrial Average /quotes/comstock/10w!i:dji/delayed (INDU 10,401. -119.10, -1.13%) was off 108 points, or 1%, at 10,413, while the Standard & Poors 500 /quotes/comstock/21z!i1:inx (SPX 1,115. -12.76, -1.13%) dropped 1.5% to 1,112. Earlier, the Dow was down as much as 273 points. The moves follow a volatile Thursday when the Dow fell nearly 1,000 points midafternoon, before closing off 3.2%.

The second consecutive day of brisk market activity came amid investor worries on Europes debt crisis, lingering questions about the origins of Thursday afternoons freefall and worries about the pace of the recovery. The decline in stocks came even after a Labor Department report showing job growth at its fastest pace in four years.

The Dow is on track for a historic week. If the measure ends at 10343.33 or lower, it will be its seventh-worst weekly point drop ever. At late morning levels, the index was within distance of its largely weekly point drop since the week of Oct. 10, 2008, and its largest percentage drop since the first week of March 2009.

The action comes after one of the most tumultuous stock sessions in history.

U.S. stocks ended with steep losses Thursday after an afternoon meltdown lopped nearly 1,000 points off the Dowits biggest intraday drop on a point basis everbefore a partial recovery. The Dow finished the day down 347 points, or 3.2%.

Friday morning, the Labor Department said nonfarm payrolls rose by a higher-than-expected 290,000 last month, the largest gain since March 2006. That followed an upwardly revised 230,000 increase in March. Economists were expecting a smaller rise. The March figure was originally reported as a 162,000 increase.

Taking into account revisions to prior months, the U.S. economy added an average of 143,000 jobs a month in the first four months of the year.

However, as a reminder of the labor markets continued weakness, the unemployment rate increased to 9.9% last month. Economists were expecting it to remain at Marchs 9.7% level.

Elsewhere, the euro recovered a bit against the dollar.

The euro zones latest moves to contain Greeces debt crisis are again in focus Friday after Germany approved its contribution to a joint European Union-International Monetary Fund loan package for Greece. The finance ministers of the Group of Seven leading economies are also due to hold a telephone conference to discuss the Greek debt turmoil.

Early in the session, trading was unusually heavy. An hour into the action, New York Stock Exchange composite volume was already near its average midday levels. By 10.30 a.m. EDT, nearly 2.6 billion shares had changed hands, with nearly 95% of trading in the downward direction. By 12:30, 5.6 billion shares traded in New York Stock Exchange Composite volume, already above the years average volume of 5.02 billion, as of Tuesdays close.

Some analysts were quick to point out that unlike in late 2008, many of the factors that sent stocks plummeting are now known quantities.

It feels like investors are fighting the last war here, Keith Goddard, president and CEO at Capital Advisors, said. The banking system knows where the bodies are buried, unlike in 2008, so Im more comfortable this one wont turn into a significant route.