Sonar deployed in hunt for Indonesia ferry disaster victims

Indonesian authorities today turned to cutting-edge sonar technology as they search one of the world's deepest lakes for victims of a deadly ferry disaster.

Search teams hope the equipment, on loan from Indonesia's navy, will help find the overloaded boat which sank Monday on Lake Toba, a picturesque tourist destination in Sumatra.

Just three passengers have been confirmed dead so far, while 18 were rescued. But official estimates list 193 others -- including children -- as missing, which has raised fears that many bodies are trapped inside the ferry at the bottom of the lake.

The accident could be one of Indonesia's deadliest maritime disasters.

Despite a massive search operation involving some 400 personnel, the vessel has still not been located after four days. Lake Toba, which fills the crater of a supervolcano that exploded in a massive eruption tens of thousands of years ago, is 500 metres (1,640 feet) deep in parts, hampering the search effort. It covers some 1,145 square kilometres (440 square miles).

Sonar technology uses sound pulses to detect and pinpoint underwater objects. The advanced equipment rolled out for the search effort is powerful enough to work at the lake floor, authorities said.

"Our search target for the ship is at a depth of 500 metres," Budiawan, an official at Indonesia's search and rescue agency, told AFP. "(This equipment) can reach 600 metres."