Six people enrolled in a foreign trainee program participated in construction work at the disaster-stricken Fukushima No. 1 nuclear plant, despite the plant operator's ban on program participants working at the complex, officials said Tuesday.

The case is the latest in a string of inappropriate practices involving foreign trainees under the government's Technical Intern Training Program, often criticized as a cover to import cheap labor.

Tokyo Electric Power Company Holdings Inc. had said in February last year that it would not permit foreign trainees to work at the plant, which was crippled by the 2011 quake and tsunami disaster, even though workers in some parts of the plant are not required to wear protective gear or dosimeters.