Japan has launched a series of nationwide safety inspections after a fire killed 44 people in a building in Tokyo's red-light district Saturday. The investigation into the cause of the fire is continuing.

Seventy Tokyo police officers have been assigned to probe the exact cause of the deadly fire that raged through a four-story building in the Japanese entertainment district of Kabukicho early Saturday morning.

Police say it appears that a fire broke out and damaged a gas pipe, which caused a gas leak and then an explosion. Local Japanese media are reporting that some investigators suspect arson and the involvement of Japanese gangsters - claims that the Tokyo Metropolitan Police Department will not confirm.

Police say that while the exact cause of the blaze remains unknown, numerous safety violations contributed to the tragedy, including sealed windows and a lack of emergency exit routes.

The catastrophe - the nation's worst fire-related disaster in three decades - has sparked nationwide safety inspections of more than 6,000 buildings.

"The Fire Department has started inspections of multi-tenant buildings similar to the one where the fire took place," said Michiko Horiuchi, a spokeswoman for the Tokyo Fire Department. "They are checking evacuation routes and fire prevention equipment." Fire authorities say emergency evacuation drills had never taken place in the building where the fire occurred.

Ms. Horiuchi says building owners often ignore officials' safety recommendations. She notes that enforcement is a problem, since there are no fines or prison terms for violators. "In order to prevent further such tragedies," she said, "we will encourage building owners and managers to follow the law and maintain their properties. After this investigation is complete, we may consider tightening fire safety regulations."

Newspaper editorials also addressed the need for more rigorous safety measures. An editorial in the Asahi newspaper says authorities must find the cause of the tragedy and pursue those who are responsible.