The real estate agency managing an apartment building in Kitakyushu where six people died in a fire Sunday night had a regular policy of nearly doubling the rent for tenants who lived there for more than a month — a move intended to deter long-term stays, realtor sources said Tuesday.

The sharp rise in rent may have led to frequent turnover of residents, mainly day laborers, and contributed to the tenants' lack of awareness about fire prevention.

The agency considers the apartment a temporary living facility for day workers and welfare recipients. After residents pay ¥500 every day for one month, the agency raises the daily rent to ¥900. Some former tenants left the apartment, which is said to have been effectively a flophouse, within their one-month stay to avoid the hike.