The cause of a fire that leveled Camp Nenookaasi in south Minneapolis in late February cannot be determined because of the number of "possible ignition sources in the area of origin," investigators say.

"Due to the overwhelming amount of possible ignition sources in the area of origin and that there was still a large amount of propane containers that would need to be mitigated it was not possible to positively identify the one ignition source or the first fuel ignited," Minneapolis Fire Department officials said in a release.

Fire Department investigators will keep the case open. They'll hand off the investigation to the Minneapolis Police Department if they suspect the fire was "the result of suspicious or criminal intent."

Investigators say the fire originated in a yurt on the south side of the camp and that wind quickly spread it to the rest of the site. Neighbors said they heard explosions amid the flames when the fire erupted.

The encampment has moved several times as city workers dismantled and fenced it off in previous locations. The city of Minneapolis recently inked a deal worth nearly $1 million with a company called Helix Health and Housing Services to find long-term housing for its residents.

Many of the camp's residents were Native American. Activists allege two smaller fires that cropped up in the days before the blaze went uninvestigated.

Minneapolis City Council Member Jason Chavez, who represents Ward 9 where the camp was located, has echoed their calls for an investigation to determine whether February's fire was an accident or arson.

Star Tribune staff writers Louis Krauss and Andy Mannix contributed to this story.