"We more or less do not expect to see anything worse than what we are seeing now," said NISA's Hidehiko Nishiyama.
Power has now been restored to Units 2, 5, and 6 now that a replacement line from the United States reached the complex on Friday, and crews are working to restore power to Unit 3. It's still unclear when they will turn the power on and restart the cooling systems.
There is still no new information regarding the spent fuel pool at unit 4, and it appears that they have yet to begin dousing it with water.
Low levels of radiation have been detected well beyond Tokyo, which is 140 miles south of the plant, but according to Japanese officials hazardous radiation levels have been limited to the plant itself.
Fears that radiation from the Fukushima Dai-ichi nuclear facility will reach the West Coast of the United States have caused alarm since last week, and it was recently confirmed that the plume from Japan did arrive in California.
"Radiation is very scary. You can't see it and in high doses it's very, very dangerous," Philip Fine of the South Coast Air Quality Management District told "Good Morning America."
Electronic sentries have been on guard, watching for any sign of radiation spikes from that radioactive plume advancing on the west coast.
One detector in Sacramento indicated a "miniscule" amount of radiation that officials believe originated in Japan.
But the particle was miniscule -- equal to one-millionth the typical dose from natural sources like rocks or the sun.
Still, the crisis in Japan has caused a frenzy amongst some Americans who have gone into panic mode.
Potassium iodide pills and other protection from radiation poisoning have disappeared from store shelves. The frenzy has prompted the Food and Drug Administration to warn people to be aware of online scams offering fake radiation treatments.
Health experts say that real potassium iodide pills can have negative health effects, while an air quality specialist told "GMA" that breathing in smog is more dangerous than the current risk of breathing in radiation.
ABC News' David Wright and The Associated Press contributed to this report.