Five nuclear power plants and several oil refineries shut down automatically after the quake.
Officials say no radiation leaks have been reported.
Hokuriku Electric Co said all three reactors at its Onagawa nuclear plant in northern Japan were shut down.
But Kyodo news reports a fire has broken out in the turbine building of Onagawa nuclear plant in Miyagi Prefecture.
Its not immediately clear if there is a risk of a radioactive leak as a result of the fire at the plant.
Kyodo also reports that an emergency core-cooling unit had been activated at Fukushima nuclear plant, without giving further details.
Excerpted from - Japan ablaze after quake; no radiation leaks