Tons of contaminated groundwater from the stricken Fukushima nuclear plant have overwhelmed an underground barrier and are emptying daily into the Pacific, creating what a top regulator has called a crisis. The water contains strontium and cesium, as well as tritium. The plant was already struggling to store hundreds of thousands of tons of contaminated water that flowed through the buildings housing three reactors where [three] meltdowns occurred in 2011. But the contamination in this new groundwater problem is from different sources, Tepco said. The company has admitted that it failed to respond quickly enough to the latest groundwater contamination, saying it was preoccupied with more pressing issues like cooling the damaged reactors. Tepco appears overwhelmed in dealing with what is a very serious problem," said Akio Yamamoto, a professor of nuclear engineering at Nagoya University, who serves as outside expert for the Nuclear Regulation Authority, Japan's nuclear watchdog. Critics contend that the plant has emitted far more radioactive materials than it is saying, based in part on levels of contaminants discovered in the harbor, which are well above safe levels in some places. The contamination appears to be spreading, with tests last month by Tepco showing high levels of tritium and other radioactive elements like strontium starting at other locations near the two other crippled reactors.