MINNEAPOLIS — A Minneapolis duplex fire that killed five children last week appears to be accidental, investigators said Wednesday.

According to the Minneapolis Arson Unit, the cause of the fire is undetermined. But the fire department said “there is no indication of intentional acts” and nothing to indicate the fire is anything but an accident.

Five siblings, ages 8 years to 18 months, were killed and two survived along with the children’s father. A 9-year-old girl remained in critical condition Wednesday but a 5-year-old girl has been upgraded from critical to serious condition, a spokeswoman for Hennepin County Medical Center said.

The children’s father, Troy Lewis, 60, remained in satisfactory condition Wednesday.

Lewis jumped from a second-story window after the fire broke out in his rental home in north Minneapolis Friday morning. He injured his spine, but he ran back inside to save his screaming children.

Although the cause of the fire is undetermined, investigators will continue looking into possible causes, which is not uncommon following an undetermined ruling, the fire department said.

Fire officials have said 15 people lived in the duplex.

Investigators said Friday the building had no current code violations.