Officials are considering increasing the evacuation zone, saying there's no clear sense of what's causing the spike.
Radiation contamination fears are slowing recovery efforts in the 12-mile evacuation zone. It's not clear how many bodies are buried there, but the number is estimated to be in the hundreds.
"We find bodies everywhere - in cars, in rivers, under debris and in streets," a police official from the hard-hit Fukushima prefecture said Thursday.
The official death toll from the 9.0-magnitude quake and tsunami tops 11,000, with the final figure to surpass 18,000.
Meantime, the U.S. Environmental Protection Agency is increasing its monitoring of radiation after two states reported low levels of radiation in milk.
Sample recently taken in San Luis Obispo County and Spokane, Wash., show radioactive iodine at a level 5,000 times lower than the limit set by the FDA. Officials call the level "miniscule" and say it poses no risk to public health.
"Radiation is all around us in our daily lives," said Patricia Hansen, senior scientist.at the FDA. "A person would be exposed to low levels of radiation on a round-trip cross-country flight, watching television, and even from construction materials."
Dr. Richard Besser, ABC News Chief Health and Medical Editor, said the amount of radiation found in bananas is higher than the levels that were found in the milk.
The United States had already halted imports of dairy products and produce from the affected area of Japan. Other foods imported from Japan, including seafood, were still being sold to the public but screened first for radiation.
Japanese foods make up less than 4 percent of all U.S. imports.
Since the quake and tsunami struck, it has just been announced Japan's baseball season has been pushed back indefinitely. The players are using the extended off-season to help tsunami victims.
The Associated Press contributed to this report.
