Above graphic: A sketch of the home from the report. Red circle, added by The Star Tribune, shows "melted mass."

Investigators with the state fire marshal's office believe a fire that killed five children in north Minneapolis this February began in an area of the house where they recovered an unknown "melted mass," but they have not determined a precise cause of the blaze.

A February report released on Wednesday afternoon describes the detailed walk through of the home following the fire. The report said that the ignition source is not yet known because forensic testing is not yet complete.

A "melted mass of material" was located next to two love seats in a middle room of the apartment. "Raising this mass from the floor and examination of the underside failed to reveal what this mass had been," the report said.

It was in this approximate area, the northwest corner of the living room, where investigators concluded that the fire began. They did not directly implicate the melted mass, however.

Previously, a Fire Department investigation stated that a space heater had been running in the archway between the living room and dining room, the general area where the "melted mass" was found.

The mass was retained by Dan Choudek, a forensic engineer, for x-ray examination, according to the report. Choudek did not immediately respond to a message seeking comment Wednesday afternoon.

A number of stakeholders, including the family, the property owner and insurance representatives are participating in a joint investigation into the causes of the fire.

An attorney for the family, Jeff Sieben, said Wednesday that they believe the mass is a space heater. It has been x-rayed, he said, but won't be fully analyzed until a meeting in August. They have not determined a precise cause of the fire.

Investigators also found an unplugged, "older-looking" space heater with a severed cord that was separated in the middle and knotted back together. No outlets were located in the vicinity of that space heater.

In February, the Fire Department said that the cause of the fire was "undetermined." Assistant Chief Cherie Penn wrote in an e-mail Tuesday that they did not have any updates regarding the fire.

Above: Dan Choudek, a forensic engineer with Onsight Engineering, removed the remains of a space heater from the home (Elizabeth Flores)

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