Investigators are expected to focus on the flammability of cargo carried by an Asiana Airlines Boeing 747-400 freighter that crashed Thursday off the coast of South Korea in the East China Sea, killing both pilots. The aircraft was destroyed.

According to the airline and South Korean government officials, the pilots reported a fire and control problems about 1 hr. into the flight and were diverted to Jeju when contact was lost.

According to Flight Safety Foundation's Aviation Safety Network, the 747F departed Seoul Incheon at 3:05 a.m. bound for Shanghai Pudong. South Korea Deputy Transport Minister Kim Han-Young told reporters that "the crew told Shanghai traffic controllers that fire had erupted in the hold." He added, "We suspect some flammable material caught fire there."

The CF6-powered freighter was carrying 58 tonnes of cargo, including 0.4 tonnes of materials such as lithium batteries, paint, amino acid solution and synthetic resin. According to The Korea Times, Asiana CEO Yoon Young-Doo said, "We load and manage lithium batteries according to the regulations set by the International Air Transport Assn. The goods on the cargo plane were also managed according to the checklist and double-checked by the captain."

The captain had 14,123 hr. of flight time, of which 6,896 were on the 747. The co-pilot had 5,211 hr. of flight time. The aircraft that crashed had its first flight in February 2006, according to ASN.

While there is discussion about a possible cargo-hold fire, there has been no conclusion reached regarding the crash's cause, authorities stressed. U.S. FAA last year issued a Safety Alert for Operators on carriage of lithium batteries as cargo on aircraft.