Complex sentence: It is estimated that up to 10,000 civilians and prisoners of war were detained in the Velepromet camp before the camp was closed down in March 1992, upon arrival of the United Nations Protection Force to the area.
Split into simpler sentences: It is estimated that up to 10,000 civilians and prisoners of war were detained in the Velepromet camp. The camp was closed down in March 1992, upon arrival of the United Nations Protection Force to the area.