File photo of Asiana Airlines cargo planes parked at Incheon Airport, west of Seoul
The pilot and co-pilot of an Asiana Airlines cargo plane were killed when the aircraft caught fire and crashed Thursday off South Korea's southern island of Jeju, officials said.
Investigations were focusing on whether inflammable material in the hold of the Boeing 747-400 sparked the blaze, reports AFP.
The plane left the country's main international airport at Incheon at 3:05 am, bound for Shanghai's Pudong airport.
But about one hour after take-off the pilot radioed Chinese air traffic controllers in Shanghai that fire had broken out in the hold and that the plane had to divert to Jeju, transport ministry officials said.
"In its last message, the crew told Shanghai traffic controllers that fire had erupted in the hold. We suspect some inflammable material caught fire there," Deputy Transport Minister Kim Han-Young told journalists.
The plane carried 58 tonnes of cargo, including 0.4 tonnes of potentially risky materials such as lithium batteries, paint, amino acid solution and synthetic resin, he said.
A coastguard patrol boat found debris including part of the wing, seats and a liferaft just over 100 kilometres (60 miles) west of the island.
Four coastguard boats and a helicopter are searching the area.
Asiana is the country's second and smaller flag carrier. It largely operates short-haul routes into Asia.