Warehouse blaze claims 40 lives

SEOUL, South Korea (CNN) -- A massive fire swept through a newly constructed warehouse in Icheon, South Korea Monday, burning for several hours and setting off a series of explosions that killed 40 workers inside, fire officials have told CNN.

Firefighters raised the death toll after they accounted for 10 missing workers.

Ten others were hospitalized with burns and smoke inhalation, and some are listed in serious condition, fire official Shin Jong-hoon said. Seven other survivors escaped without injury, Shin said.

The fire broke out just before 11 a.m. at the refrigeration warehouse in Icheon, about 50 miles (80 km) south of Seoul.

Workers were putting refrigerants in the warehouse and getting it ready for its opening -- scheduled to take place in several days -- when the fire broke out in the basement of the two-story building, South Korea's Yonhap news agency reported.

Investigators are trying to determine what caused fire, but believe that flammable gas in the basement was ignited by a spark, immediately triggering several explosions -- witnesses reported hearing at least three blasts Monday morning.

Toxic fumes quickly engulfed the warehouse and hampered firefighters trying to enter the facility. They had to drill holes from the roof of the warehouse to the basement to let the toxic fumes and billowing smoke escape.

"We couldn't enter because of the dense smoke and the danger of the building collapsing," Shin said.

Video from the scene showed showed firefighters pouring fire-suppressant foam and water on the warehouse as gray smoke billowed into the sky.

Six hours after the fire began, the building's temperature still had not cooled enough for firefighters to search for the missing, fire official Choi Jin-jong told Yonhap. Even after 10 hours, the remains of the building were still smoldering. E-mail to a friend

CNN's Kathy Paik and Sohn Jie-ae contributed to this report

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