Consumer price index dropped unexpectedly in April

Energy prices reflected big declines in April, dropping 1.4 percent, while gasoline prices fell 2.4 percent. Food prices made a modest 0.2 percent advance. 

Low inflation could raise concerns of deflation but it's unlikely, as the economy continues to show signs of recovery. 

Inflation has remained in check since the recession began in December 2007, allowing the Federal Reserve to keep interest rates historically low — near zero — to provide an impetus for economic expansion. Fed officials have expressed the need to keep interest rates low for the foreseeable future, while acknowledging they could change rates at any time if the economy warrants.