The fire broke out during the night of August 31 at the tent camp in Högdalen, in southern Stockholm. It was said to have started to burn in four different places at the same time. One man who was badly burned died weeks later from his injuries.
Police are now investigating whether any criminal intent was behind the fire.
Originally, officers classified the blaze as second-degree assault, whereby the fire was started accidentally by residents. They also did not cordon off the charred campsite for a forensic exam until a number of hours later.
Now the department's internal investigation is reviewing the case to see if police have done anything wrong.