( CNN ) -- Tests detected low levels of radioactivity on 17 U.S. Navy helicopter crew members when they returned to the USS Ronald Reagan after conducting disaster relief missions in Japan , the military said Monday . No further contamination was detected after the crew members washed with soap and water , the Navy said . In addition , the Navy said the U.S. 7th Fleet has temporarily repositioned its ships and planes away from the Fukushima Daiichi nuclear power plant after detecting low-level contamination in the air and on its planes in the area , the Navy said . One ship was operating about 100 miles northeast of the power plant when `` airborne radioactivity '' was detected , the Navy said . The Navy 's statement , however , provided some perspective , noting that the maximum potential radiation dose received by personnel when the ship passed through the area was `` less than the radiation exposure received from about one month of exposure to natural background radiation from sources such as rocks , soil , and the sun . '' On Sunday , the USS Ronald Reagan started delivering aid in the coastal regions of Japan 's Miyagi prefecture . Crew members , in conjunction with the Japan Maritime Self Defense Forces , conducted 20 sorties delivering aid pallets . Eight U.S. and Japanese helicopters were used to distribute the pallets , according to Sgt . Maj. Stephen Valley of U.S . Forces Japan . Workers are scrambling to cool down fuel rods and prevent a full meltdown in three reactors at the earthquake-hit plant . Radioactive steam has been released , intentionally to lessen growing pressure in the reactors .
The Navy says washing with soap and water removed the radioactivity . The U.S. 7th Fleet moves ships and planes away from the Fukushima Daiichi plant . The Navy says `` airborne radioactivity '' was detected 100 miles away from the plant . The most exposure anyone onboard received is less than a month 's normal radiation dose .