The Japanese government is investigating how radioactive concrete ended up in a new apartment complex in the Fukushima Prefecture, housing evacuees from a town near the crippled nuclear plant.

The contamination was first discovered when dosimeter readings of children in the city of Nihonmatsu, roughly 40 miles from the reactors at Fuksuhima Dai-ichi, revealed a high school student had been exposed to 1.62 millisieverts in a span of three months, well above the annual 1 millisievert limit the government has established for safety reasons. Further investigation traced the radiation back to the student's three-story apartment building, where officials detected radioactive cesium inside the concrete.

Radiation levels at the 6-month-old apartment were higher inside the building than outside. A dozen families live in the new apartment complex.

The gravel used in the cement came from a quarry in the town of Namie, located just miles from the Fukushima plant. While Namie sits inside the government mandated 12-mile "no-go" zone because of radiation concerns, it wasn't completely closed off until the end of April, meaning the gravel was exposed to radiation spewing from the Fukushima plant during that time.

The owner of the quarry said he shipped 5,200 tons of gravel to 19 different companies, two of which now say they sold the material to 200 construction firms. The Ministry of Economy, Trade, and Industry has launched an investigation to determine where the gravel was used.

The contaminated concrete is the latest radiation scare that has plagued Japan more than 10 months after a catastrophic earthquake and tsunami triggered the worst nuclear accident since Chernobyl. 80,000 people have been displaced by the Fukushima disaster, many of whom may never return home.

"We thought we could finally settle here. I have no words," said a resident, who told broadcaster NHK  she moved to the apartment with her husband and young children, to escape radiation. "I just feel so awful for my kids. I feel like I've failed as a parent."

NHK reports government officials brushed off initial inquiries about the contaminated concrete in December, saying they had conducted thorough checks.