Minneapolis investigators say the cause of a fire that killed three young children has not been determined.

The Minneapolis Fire Department said in a statement Wednesday that while the cause cannot be proven, the fatal fire remains under investigation.

Later Wednesday, the Hennepin County medical examiner’s office officially identified the young victims, as Latoria Thomas, 5, Latorious Thomas, 6, and Latorianna Thomas, 1. The cause of death for all three was listed as “inhalation of products of combustion and thermal injuries.”

Investigators say the fire Saturday is believed to have started in the kitchen area and the children’s mother, Taneisha Stewart, has said she had turned on the oven for warmth because the furnace wasn’t working.

A vigil was held Tuesday and a memorial service was planned for Wednesday night in Robbinsdale.