SEOUL, Feb. 15 (Xinhua) -- Two were detained and 16 booked for investigation on Friday in a probe into a warehouse fire that left 40 people dead last month, while the cause of the blaze is still undetermined, police said.

    The fire ripped through a two-story refrigerating warehouse, Korea 2000, that was under construction in Icheon, Gyeonggi province, leaving 40 dead and 10 others injured. Most victims were daily wage earners, some from China.

    Wrapping up its 40-day probe, the Gyeonggi Provincial Police Agency said it took into custody a supervisor and fire prevention manager of Korea 2000 for alleged misconduct, while booking 12 others, including the warehouse owner, for investigation without physical detention on charges of misconduct, negligence, bribery and violation of fire prevention laws.

    Four firefighters were also booked for allegedly taking a bribe from a fire prevention firm or for being negligent.

    The cause of the fire is yet to be determined because all facilities in the suspected area of the fire's origin were badly burned, police said. They suspect the explosions stemmed from flammable gas that was ignited by stray sparks from a welder's torch.

    Police said they asked experts to conduct a simulation test to define the cause.

    Poorly equipped with firefighting equipment, the warehouse was vulnerable to a man-made disaster, investigators said. Its basement, about the size of a football field, has only two exit doors. A 224-ton water tank and sprinklers were useless because they were destroyed by the explosions. Most workers inside the warehouse were installing pipes and arranging electric facilities at the time.