TOKYO (AP) — Japan's top nuclear regulator is raising safety concerns about hastily built storage tanks and their foundations after reports of new leaks of radiation-contaminated water.

Nuclear Regulation Authority Chairman Shunichi Tanaka says a small leak and signs of other possible leaks have been spotted at several other storage tanks at the Fukushima Dai-ichi nuclear plant.

Officials say some contaminated water has escaped into the sea. The plant was damaged in Japan's 2011 earthquake and tsunami.