The U.S. consumer price index fell 0.7 percent in January to take the 12-month inflation rate into negative territory for the first time since 2009, the Labor Department reported Thursday.

The CPI declined 0.1 percent over the 12 months ending Jan. 31.

Core CPI, which excludes more volatile food and energy prices, rose 0.2 percent in January and 1.6 percent over the 12-month period.

Last month's drop in the CPI, which followed declines of 0.3 percent in November and 0.4 percent in December, was larger than analysts expected.

Energy prices fell 9.7 percent in January, while gasoline prices plunged 18.7 percent, the biggest fall in seven consecutive months of declines, the government said.

The Federal Reserve has expressed concern because inflation in the United States remains below the 2 percent annual the central bank healthy.

Fed Chair Janet Yellen acknowledged this week in congressional testimony that as the overall economic performance improves in the United States, the first raise in interest rates since December 2008 becomes more probable. EFE