Passengers arriving at New York-area airports from Japan are being screened for radiation as a precaution because of the nuclear crisis unfolding in that country.
"It is possible that we will see passengers with detectable radiation levels in New York-area airports as travel from Japan continues," the New York City health department told NBC New York. "The contamination is detectable, but does not pose a public health risk to passengers or anyone that they come into contact with."
Authorities said any radiation would have to be in significant amounts to pose any health risk.
One passenger told NBC New York that everyone on Delta Flight 172 from Tokyo to John F. Kennedy Airport was told in an announcement onboard that "all passengers would have to go through radiation screening."
"I was nervous about it -- I was worried they might send me back to Japan if they found radiation on me," passenger Marisa Dargahi said after landing.
Customs and Border Protection said there have been reports of radiation being detected from some cargo arriving from Japan at several airports.
Those airports include Chicago, Dallas and Seattle. Radiation has not been detected in passengers or luggage. And none of the reported incidents involved dangerous or harmful amounts of radiation.
No harmful levels of radiation have reached the U.S. since the nuclear crisis in Japan sparked by last week's devastating earthquake and tsunami, she said.
New York State Health Commissioner Niray Shah says no states are expected to experience harmful levels of radiation and around the region there is no reason to buy or use potassium iodide.
CBP, which monitors ports, routinely screens passengers and cargo for radiation. Agents have been advised this week to pay particular attention to arrivals from Japan.
The agency handles more than half a million radiation alarms a year, though many are related to medical procedures.
Napolitano said the screening of passengers and cargo is being done "in an exercise of caution."