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Associated Press
The inside of the tsunami-crippled No. 4 reactor building is seen during a press tour at Tokyo Electric Power Co.'s (TEPCO) Fukushima Dai-ichi nuclear power plant in Okuma, Fukushima Prefecture, Japan, Saturday, May 26, 2012.(AP Photo/ Toshiaki Shimizu, Japan Pool) JAPAN OUT

TOKYO — Japan's environment and nuclear minister visited the tsunami-crippled Fukushima Dai-ichi nuclear power plant on Saturday to inspect a spent fuel pool at the center of safety concerns and said it appeared to have been properly reinforced.

The visit by Goshi Hosono, apparently aimed at demonstrating the safety of the facility, came amid renewed concerns about conditions at the plant's No. 4 reactor after its operator reported a bulging of the building's wall. Nuclear regulators ordered a new investigation and seismic tests of the building and its pool.

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The building was damaged by an explosion and fire soon after the Fukushima plant was hit by a massive magnitude-9.0 earthquake and tsunami on March 11, 2011. The pool remains one of the plant's biggest risks due to its vulnerability to earthquakes.

The plant's operator, Tokyo Electric Power Co., has reinforced the structure and says it now can withstand temblors as strong as last year's quake.

A small group of journalists was allowed to enter the reactor building for the first time with Hosono. Inside were piles of broken wall panels, pieces of cement and mangled equipment, showing the magnitude of the explosion.