The U.S. Air Force's WC-135 Constant Phoenix aircraft, capable of detecting nuclear explosions, deployed to the United Kingdom last week for a routine mission, the service said Wednesday.
The "nuke hunter" plane, also known as the "sniffer," is on a "pre-planned rotational deployment scheduled in advance," Air Force spokeswoman Erika Yepsen told Military.com.
The WC-135 "regularly flies around the world for missions," added Col. Patrick Ryder. "Any of the reporting in terms of having another reason [is] not grounded in fact," the service's chief spokesman said.
There has been ongoing speculation the U.S. sent the detection aircraft to Europe after an alleged Russian nuclear test, which caused radioactive levels to "spike" in areas such as Norway, according to The Aviationist blog, which first tracked the aircraft Feb. 17.
The aircraft belongs to the 45th Reconnaissance Squadron, 55th Operations Group, at Offutt Air Force Base, Nebraska.
According to the The French Radioprotection and Nuclear Safety Institute, a research organization and environmental protection advocacy agency that tracks nuclear activity throughout the globe, trace amounts of Iodine-131 (131I) -- a radioisotope of iodine that has a radioactive decay half-life of about eight days -- were detected in Norway, Finland, Poland, the Czech Republic, Germany, France and Spain throughout January.
The presence of Iodine-131 "is proof of a rather recent release," the organization said.
Government agencies have not come forward to explain the radiation. Experts, however, say the leaks are not a mystery.
Scientist Jayde Lovell, host of TYT network's ScIQ and executive director of ReAgency, a PR firm that specializes in science storytelling, told the International Business Times UK, "Iodine-131 is not a mystery.
"It's released in low levels normally as part of nuclear power and, since nuclear power is common throughout Europe, it's not unusual to be able to detect trace amounts during certain types of weather, particularly the cold weather of a European winter," she told the newspaper.
"I would be expecting to see a lot more and more different kinds of radiation than just Iodine-131 if it was a nuclear test," Lovell said.
Apaches to Europe
Meanwhile, the Air Force also delivered AH-64 Apache helicopters to Ramstein Air Base, Germany, on Wednesday, according to a release from European Command. Air Mobility Command's C-5 Galaxy transport aircraft are also expected to deliver UH-60 Black Hawks to Latvia by the end of the month for missions as part of Operation Atlantic Resolve, the release said.
The helicopters will be maintained by the Army's 10th Combat Aviation Brigade to ensure "we have additional combat firepower and support if needed at the time and place of our choosing," said U.S. Army Col. Todd Bertulis, EUCOM's deputy director of logistics.
"The continued rapid and responsive logistics efforts of Operation Atlantic Resolve should assure our European allies in maintaining a Europe that is whole, free, prosperous and at peace," he said in the release.
The Apaches, from Fort Bliss, Texas, and Black Hawks, from Fort Drum, New York, will be a part of a nine-month rotation under Atlantic Resolve, the U.S. effort launched in April 2014 to reassure partners and allies after Russia's incursion into Ukrainian territory and annexation of Crimea.
The Army intends to use the helicopters throughout Germany, Latvia and Romania, the release said.