Yomiuri Shinbun (in Japanese; 4:35PM JST 3/23/2011):
According to TEPCO, gray smoke is rising from the Reactor 3 since 4:20PM (JST). The workers have been evacuated from the area.
TEPCO says "The smoke looks grayish. We don't know whether it's from the turbine building or the reactor building."
Gray smoke was also seen on March 21 around 3:55PM, rising from where the Spent Fuel Pool is located in the Reactor 3.