Officials at the Fukushima Daiichi Nuclear Plant say they've made a troubling discovery. Workers have detented a surge in the amount of radioactive cesium in a well at the facility in recent days. Tokyo Electric Power Company officials regularly monitor groundwater around the reactor buildings. They check for radioactive substances and analyze their effect on the environment. On Monday, workers found 9,000 beck rolls of cesium-134 per liter of water in an observation well, and 18,000 beck rolls of cesium-137. The well is located between the number two reactor and the ocean. The amounts were about 90 times higher than on Friday. Tepega officials say they can't explain the sudden jump. They're also unsure how the cesium is affecting the ocean. Workers have detected increasing amounts of radioactive substances in seawater near the plant since May. Example taken last week contained the highest concentration of radioactive tritium recorded in more than two years. Workers at Japan's damaged nuclear plant have detected a spike in levels of radioactive substance in nearby seawater. The plant's operator says it's the highest reading for tritium offshore in two years. Tokyo Electric Power Company workers collected water from a port near the Fukushima Dij plant on Wednesday. They found it contained 2,300 beck rolls of tritium per liter. Thus twice the amount detected about two weeks ago and the highest since monitoring began in June 2011. But they say the figure is still well below the government's safety limit. Tepega workers also tested water collected from a well near the port. They found it contained a record level of radioactive substances 900,000 beck rolls per liter. Tepega officials say they can't roll out the possibility that contaminated groundwater seeped into the sea. They say they plan to build more observation wells and they'll solidify the ground to prevent the water reaching the ocean.