© JiJi Press/AFP/Getty Images
This aerial view shows the quake-damaged Fukushima nuclear power plant in the Japanese town of Futaba, Fukushima prefecture on March 12, 2011.

Japanese officials confirmed Monday that nuclear fuel rods appear to be melting inside three reactors compromised by Friday's earthquake, though nuclear experts differ on whether the outer chamber of a reactor melting in fact constitutes a partial "meltdown."

Chief Cabinet Secretary Yukio Edano said Monday that "although we cannot directly check it, it's highly likely happening."

Unit 3 of the Fukushima Daiichi Nuclear Power Station in northeastern Japan exploded earlier Monday, wounding 11 workers; it had been under emergency watch for an explosion after a hydrogen blast at Unit 1 of the plant on Saturday. Edano said the Unit 3 reactor's inner containment vessel was intact.

More than 180,000 people have been evacuated from the area, and as many as 1,500 have been examined for radiation, according to USA Today.