The aircraft carrier USS Ronald Reagan and other US Navy ships in the waters off the quake zone in eastern Japan were repositioned after the detection of a low-level radiation plume from the troubled Fukushima nuclear plant located 100 miles away.
According to 7th Fleet Commander and Spokesman Jeff Davis, the ships were moved away from the downwind direction of the plant as a precautionary measure on Sunday.
The carrier is one of seven US Navy ships that were quickly moved to the eastern coast of Japan to assist with relief operations after Friday's earthquake and tsunami.
The ship's crew was exposed to a very low level of radiation.
"The maximum potential radiation dose received by any ship's force personnel aboard the ship when it 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," Davis said.
According to Davis, the radiation was first detected by air particulate detectors aboard three helicopters located 60 miles away from the shoreline.
The helicopters were returning to the carrier from a relief mission to the quake and tsunami ravaged city of Sendai.
Detectors aboard the USS Ronald Reagan also sounded while it was located 100 miles north east of the Fukushima Daiichi Nuclear Power Plant. Low amounts of radioactive materials have been released into the atmosphere as plant officials desperately try to prevent a meltdown of the nuclear cores at two of the plant's reactors.
Davis said the source of the radiation was a radioactive plume emitted by the plant.
After the helicopters landed on the carrier, radioactive contamination was found on the exterior surface of three aircrafts.
Following decontamination protocols, the 17 crewmembers aboard and the three helicopters were tested and found to have been exposed to low levels of radiation.
Most of the radiation was found on the crewmembers clothes, but radiation was detected on the skin of one of the crewmembers.
The low level radioactivity from affected personnel was removed by washing with soap and water. Their clothes were also discarded.
They were subsequently surveyed and no further contamination was detected.
A US official said the ship has now moved north, away from where the radiation was detected and the ship's helicopters are not flying until a mitigating strategy to reduce exposure to the ships' crews is determined.
Davis stressed that the commitment to the relief mission will continue.
"We remain totally committed to our mission of providing assistance to the people of Japan," he said.