The U.S. is sending chartered planes to Japan to take Americans out of the country or relocate them to "safe havens" elsewhere in Asia to escape radiation exposure.
The first flight left Tokyo today, and one or two more are scheduled for Friday.
The U.S. has also sent 14 buses to the tsunami ravaged city of Sendai to evacuate 600 Americans who have been trapped by destroyed or debris clogged roads. They will be put up in Tokyo hotels for the night and be given the option of boarding one of the chartered flights out of the country.
In addition, Homeland Security is screening some planes, cargo and passengers returning from Japan for possible radiation contamination.
"We have seen no radiation by the way on incoming cargo or passengers that comes close to reaching a harmful level," Homeland Security Secretary Janet Napolitano said today.
Narita International Airport which serves Tokyo has been jammed with foreigners for the last two days as they stream out of the country or to cities further south and further away from the crippled reactors in Fukushima.
Temple University in Philadelphia announced it was taking its 200 American students from the school's Tokyo campus out of the country on a chartered flight to Hong Kong.
The State Department issued a travel warning authorizing the voluntary departure for family members and dependents of U.S. government employees in northeast Japan - Tokyo, Nagoya and Yokohama. Family members of American military personnel are authorized to board the charter flights.
Despite rising concerns, the first flight out of Narita had about 100 people aboard and was not full.
The State Department said Americans who are not government employees can also get on the flights which will take them to safe havens that at the moment are Seoul, South Korea and Taipei, Taiwan.
Travelers must make their own way home after being taken to the safe haven. They can board the charter flight in Japan without paying, but will be expected to reimburse the government for the cost of the trip at a later date.
Americans are limited to one suitcase and a small carry-on bag, and no pets are allowed, the State Department said.
In an indication of how much demand there will be for the chartered planes, the State Department said in a message to Americans in Japan, "be prepared for a substantial wait at the airport. Travelers are advised to bring food, water, diapers and other necessary toiletries with them to the airport."
The hurried exit of many foreigners is being fueled by the lack of information being put out by the Japanese government along with the more dire warnings issued by the American and European nuclear experts.
Japan said people should stay at least 19 miles away from the crippled Fukushima plants while the U.S. said 50 miles was more prudent. The two governments have given differing levels of radiation coming from the reactors.
The U.S. was urging its citizens to get far away from the reactors.
"Since the continued or increased release of wind-blown radioactive material cannot be ruled out, American citizens in Japan are advised to take prudent precautions against potentially dangerous exposure," Under Secretary of State for Management Patrick Kennedy told reporters.