As earthquake-stricken Japan struggles to prevent total nuclear meltdown, the University of Minnesota has called for all seven of its students studying in Tokyo to return home.

Four University students studying in Nagoya and Hiroshima âÄî both in southern Japan and farther from the embattled nuclear sites âÄî will be allowed to stay unless conditions in those cities deteriorate.

Among the factors in the UniversityâÄôs decision to call the students home were the looming threat of nuclear radiation, the possibility of earthquake damage to housing and teaching facilities and the spotty availability of electricity and transportation services, University spokesman Dan Wolter said in an e-mail Friday morning.

Tokyo sits along the Japanese coast about 140 miles south of the damaged Fukushima nuclear power plant where Japanese officials have been working for nearly a week to prevent a meltdown at damaged reactors and to contain spent nuclear fuel in cooling pools.

JapanâÄôs nuclear safety agency has raised its assessment of the crisis to a 5 on the international scale (which goes to 7), putting it at the same level as the 1979 partial meltdown at Three Mile Island in Pennsylvania, but below the Chernobyl disaster, which earned a 7 on the scale.

The US State Department began flying Americans out of Japan to various âÄúsafe havenâÄù locations across Asia on Thursday.

The department has also issued a travel warning for Japan and has âÄústrongly urgedâÄù Americans to leave that country.