A series of nuclear reactors continue to deteriorate at the Fukushima Daiichi plant, raising worries of a nuclear meltdown.

After two hydrogen explosions in three days at the Fukushima Daiichi plant, a third reactor has lost its ability to cool. Officials are increasingly concerned about unit 2 at the plant.

"They continue to work hard to raise the water level to cover the fuel. Let's pray again," Tatsujiro Suzuki, vice chairman of Japan's Atomic Energy Commission, posted on Facebook today.

The fuel rods on unit 2 have been fully exposed for the second time today, a dangerous development in the effort to stop the reactor from melting down. Japanese officials said that a closed steam vent has caused a dip in the water levels, allowing the rods to be exposed, the Associated Press reported.