Henry Bambang Soelistyo, the National Search and Rescue chief, said Wednesday that the finding by an Indonesian survey ship is the first major sighting of the remains of Flight QZ8501.

“Today, we successfully discovered the part of the plane that became the main aim since yesterday,” said Soelistyo, adding, “I can ensure that this is part of the tail with the AirAsia mark on it.”

The finding could give the investigation a clue to solve the mystery of what caused the crash on December 28.

Rescue workers have so far recovered 40 bodies and smaller pieces of the aircraft, including seats and an emergency door, from the sea surface. Officials are hopeful many of the remaining 123 corpses will be found entombed in the body of the plane.

On December 28, 2014, the AirAsia Airbus A320 disappeared en route to Singapore from Surabaya in Indonesia, with 155 passengers and seven crew members on board. The plane, belonging to the Malaysian airlines, was later found to have crashed in the Java Sea under yet unknown circumstances.