Police in Hokkaido said Friday they are set to investigate fire protection measures taken at a home for welfare recipients in Sapporo after a blaze gutted the lodging, leaving 11 people dead and three others injured.

The police in Japan's northernmost prefecture said they suspect the operator of the decrepit wooden building that housed 16 poor people in their 40s to 80s was guilty of professional negligence resulting in death and injury, as it failed to prevent the disaster.

According to the company that ran the facility, each of the 16 rooms of the three-story building had a fire alarm installed but no sprinklers.

The home effectively functioned as a low-cost shelter for poor elderly people. Of the 16 residents, 13 were receiving welfare, according to the local government. Among them were dementia patients, people with no relatives and some needing assistance in daily life.

A resident of the facility who escaped the fire that had started late Wednesday night told police that the blaze spread within a few minutes after a fire alarm went off, investigators said.

A corridor and area near the kitchen on the first floor of the nearly 50-year-old building, located about 1.5 kilometers north of Sapporo railway station, were particularly badly burnt, they said.

Eight men and three women died in the blaze that was brought under control about 12 hours later. The three injured residents are not in a life-threatening condition.

Fire protection measures have been problematic for facilities providing accommodation for low-income earners as such buildings are generally made up of a cluster of small rooms. The operators are reluctant to spend too much money on equipment as it would lead them to charge higher rents.

Local fire authorities said Thursday the facility was not obliged to install sprinklers by law, as it was deemed similar to a boarding house or apartment building.

But the Sapporo city government said it will examine whether the facility could have been categorized as a nursing home, since the operator provided meals to elderly residents.

If the authorities regard the building as equivalent to an elderly care facility, it should have been equipped with more fire safety measures such as the installation of guidance lights.

If such facilities have a certain percentage of residents who cannot escape by themselves, they are obliged to install sprinklers.

The Sapporo municipal government, meanwhile, has started on-site inspections of other homes managed by the same company in the city to see whether firefighting measures are sufficiently implemented.

At least 40 such homes for impoverished people in Sapporo are subject to the inspections, firefighters said.

The Ministry of Health, Labor and Welfare also dispatched officials to Sapporo to check on the city's engagement with the facility operator.