The Winnipeg house where five family members died in a fire last month had a working smoke alarm, but it was not in the part of the house where the fire began, according to fire officials.

The smoke alarm was working inside the Woodlark Place house when the fire began in a couch in the basement early in the evening of Jan. 24, Manitoba acting fire commissioner David Schafer told CBC News on Wednesday.

But Schafer said the device was installed on the main floor of the house, and there was no fire alarm in the basement.

By the time the smoke alarm on the main floor went off, it was too late for the two women and three young children inside the house, Schafer said.

"When they did finally discover it, they were quickly overtaken by the toxic fumes and smoke and heat and unfortunately weren't able to exit," he said in an interview.

Hamid Farooq, who was working on the night of the fire, lost his wife Zebunesa Sadiq, 33, his mother Shemeem Akhtar, 60, and his daughters nine-year-old Fayza Peyawary, four-year-old Aliza Sadiq. Four-month-old Hoorya Farooq died in hospital several days later.

Schafer said the family members were found in the main living area of the house. They had died of smoke inhalation.

"It's really important, if we're going to get anything out of this, for people to understand it's important to have smoke alarms on all levels of your house, as well as the sleeping areas," Schafer said.

Fire officials have officially recorded the cause of the Woodlark Place fire as undetermined, as investigators could not determine exactly how it started.