North Korea has started dismantling a large prison in the east coast city of Hamhung, NK Pro analysis of satellite imagery has found, possibly ahead of renovation after similar projects at three other prisons in the last year.

Planet Labs imagery shows about a dozen buildings have been demolished inside the walls of the prison in northern Hamhung known as “Kyohwaso No. 9” since mid-February. 

The kyohwaso facility can hold around 2,000 male prisoners, according to a 2016 book published by the Database Center for North Korean Human Rights (NKDB). 

Defectors told NKDB the prisoners held