The long-term detainment of foreign nationals at immigration centers in Japan is an infringement upon human rights and it's a growing problem, the country's bar association warned Wednesday.

Confinements for over six months were on the rise at the Omura Immigration Center in Nagasaki Prefecture with no reasonable explanation given for the detentions, the Japan Federation of Bar Associations said in a news conference. The immigration center has been under scrutiny after the death in June of a Nigerian man who went on a hunger strike to protest his detainment. He had been detained since July 2016.

As of the end of June, the number of foreign nationals who have been detained at immigration centers totaled 1,253, of which 679 had been in detention for over six months, according to the Immigration Services Agency.