US STOCKS-Yellen warning, interest rate anxiety send Wall St lower
* Yellen: Risks "moderated, not elevated," no bubbles forming
* Fed's Lockhart calls middle-of-year rate hike appropriate
* Tech stocks weigh; Apple down for third session
* Indexes down: Dow 0.9 pct, S&P 0.8 pct, Nasdaq 0.8 pct (Updates to afternoon with extension of losses)
By Noel Randewich
May 6 (Reuters) - U.S. stocks added to losses on Wednesday afternoon and the Dow sank into negative territory for 2015 after U.S. Federal Reserve Chair Janet Yellen warned of high valuations, adding to anxiety about future interest rates and a global bond rout.
The S&P 500 dipped to its lowest since early April after Yellen said high equity valuations could pose dangers, although she also said she does not see any bubbles forming.
Atlanta Federal Reserve bank president Dennis Lockhart said he still expects it will be appropriate to raise interest rates some time in the middle of the year, and that market expectations of a September increase were in "reasonable alignment" with the central bank's likely path.
His and Yellen's comments came as investors try to pinpoint when the Fed will begin raising interest rates for the first time since 2006. An April payroll report later this week may affect when the Fed will make its move. Continuación...