Moscow dispatched technical experts to Baku after some 300 Azerbaijanis perished there on Saturday in the world's worst subway disaster when a malfunctioning electrical system sparked a fire. TIME's Yuri Zarakhovich reports that it was not the fire itself, but noxious fumes that killed most of the victims. The fumes were emitted by below-standard subway construction materials that should never have been used. "That train car had just been serviced," says Zarakhovich, "and this tragedy can be attributed to technical incompetence. It's not that the materials were bad -- they were used improperly." Zarakhovich says little money or technical expertise currently exists in Russia to modernize outdated and shoddy Soviet-era construction. "The problem is widespread. There have been quite a number of accidents in Moscow and elsewhere involving subways, elevators, escalators, and roads. Given the lack of resources to combat the problem, Soviet-era infrastructure will pose significant risks for some time to come."