The blaze that killed five young siblings on Valentine’s Day was an accident, but the cause is undetermined.

The ruling Wednesday by the Minneapolis Fire Department found that the source of the fire could not be “proven to an acceptable level of certainty,” though authorities said it does not appear to be arson and will continue looking into possible causes.

A source with knowledge of the investigation told the Star Tribune that the Fire Department was examining a space heater on the second floor as a potential cause, and an investigator was seen Wednesday removing part of a heating device from the burned-out north Minneapolis duplex.

Troy Lewis, the father who survived the fire, has said a space heater he bought recently may have sparked the blaze.

Investigators from the city, the state and an insurance company combed through the site at 2818 Colfax Av. N. all morning Wednesday, snapping pictures and collecting evidence.

“There is nothing to indicate that this is anything other than an accident, and there is no indication of intentional acts,” the department said in a statement later in the day.

On Friday, five children died and two survived when the duplex went up in flames shortly after 5 a.m. The children — Christopher, 8; Mary, 6; Fannie, 4; Troy, 3, and Gwendolyn, 18 months old — died from fire-related injuries.

Lewis described his frantic efforts to rescue the children, wailing: “I wanted to get all of my babies. All of my babies.”

One of the surviving sisters, 5-year-old Electra, was upgraded from critical to serious condition on Wednesday. Her sister, Shaca, 9, remained critical at Hennepin County Medical Center. Lewis, 60, was there in satisfactory condition.

“He seems to be pretty decent healthwise ... just still in a state of shock,” said the Rev. Jerry McAfee, who visited Lewis on Wednesday.

Space heaters, portable and stationary, were responsible for a third of all home fires and 81 percent of home heating fire deaths from 2007 to 2011, according to the National Fire Protection Association.

Space heater fires are typically caused by flammable material being placed on top of or too close to them, said Lorraine Carli, a spokeswoman for the NFPA. She said the organization recommends having at least three feet of distance between a space heater and something that could burn.

Friday’s deadly fire is yet another in Minneapolis for which investigators were unable to determine a cause.

The Fire Department has still not identified what sparked a New Year’s Day fire that killed three people and leveled an apartment building and grocery in Cedar-Riverside.

And local and state investigators could not determine what caused a fast-moving apartment fire above McMahon’s Irish Pub on April 2, 2010. Six people — three adults and three children — died in that fire, the city’s deadliest in a quarter-century. The finding came after weeks of investigation of the gutted apartments at 3001 E. Lake St. and laboratory analysis of evidence.


Staff writer Brandon Stahl contributed to this report.