Investigations into the cause of a fire that destroyed a 35-storey residential high-rise in the Philippines on 14 April are ongoing, amid speculation that welding work was being carried out on the top floors. The blaze caused damages estimated at close to PHP4bn ($80m). Firefighters are also looking into how the fire spread from the top to the bottom of the building, including theories that ash and embers may have entered the structure through pipes. An incomplete fire detection and prevention alarm system has also been suggested as a possible cause of the rapid spread of the flames.