Wall St. stocks volatile after Fed holds steady on rates

Fed Chair Janet Yellen was due to hold a press conference at 2:30 p.m ET (1830 GMT). The news left investors still trying to figure out the timing for the Fed's first benchmark rate increase since 2006. Uncertainty about when the Fed will shift gears has dogged Wall Street for months - a situation that has been complicated in recent weeks by market turbulence linked to slowing growth in China and worries about the health of the global economy.