Japan is tightening restrictions on the 20km exclusion zone around the stricken Fukushima Daiichi nuclear plant, making it illegal to enter.
The move was announced by Prime Minister Naoto Kan and comes into effect at midnight on Thursday.
People were urged to leave the area shortly after the 9.0-magnitude earthquake and tsunami on 11 March crippled the plant in northeast Japan, but the order was not enforced by law, the BBC reports.
The tsunami knocked out power systems at the plant, causing cooling systems to fail and radiation leaks.
Brief re-entry will be allowed to the area's 80,000 former residents to collect belongings.
The BBC reports it is not clear how many people are living in the evacuation zone, but reports said police had counted at least 60 families.
After the disaster the government also declared a wider 10km zone around the 20km evacuation area where people should either stay indoors or leave.
It later recommended that people also evacuate that area also.