Four confirmed dead, 18 rescued after wooden ferry, reportedly operating illegally, sank off North Sumatra on Monday.

Divers and an underwater drone have joined a fleet of rescue vessels in Indonesia’s search for at least 192 passengers missing, two days after an overcrowded wooden ferry sank in one of the world’s deepest volcanic lakes in Sumatra.

Four were confirmed dead and 18 survivors were picked up from Toba Lake, but officials fear the death toll could be much higher.

Authorities are still unable to confirm how many were on board when the vessel sank on Monday in bad weather, since it did not have a manifest.

Earlier on Wednesday, the head of the local disaster agency, Mahler Tamba, told DPA news agency that a search and rescue party found an unidentified body on Wednesday morning.

About 350 rescue personnel were involved in the search.

It is possible many of the victims were still inside the sunken ferry, said North Sumatra province police chief Paulus Waterpau.

“Many survivors told authorities that less than half of them had jumped into the water before the boat sank,” he told AP news agency.

The boat was five times over its passenger capacity and equipped with only 45 life jackets, National Search and Rescue Agency chief Muhammad Syaugi told a news conference.

Survivor Juwita Sumbayak, from Medan, said she had crossed the lake many times on the same boat but on Monday it was terribly overcrowded because of holidays for the end of the Muslim holy month.

Weak enforcement of safety regulations are often blamed for ferry tragedies in Indonesia [AP]

‘I jumped, I cried with fear’

In an interview with AP, a distraught Sumbayak wept uncontrollably and called out the names of her husband and children who she believed drowned inside the boat.

She said that about 20 minutes into the journey, strong, high waves caused the ferry to list to the right and take on water, sparking a panic among passengers.

It was then struck hard by more waves and an empty small wooden boat. The ferry seemed to shake, Sumbayak said, then suddenly capsized.

“Many passengers without a life jacket jumped into the deep lake, but others drowned with the boat,” she said. “I jumped, I cried with fear.” She saw dozens of people in the water “but nobody can help.”

Suwarni, whose 20-year-old son and his girlfriend were on the ferry, slammed the search and rescue operation as slow and insufficient.

“Millions of questions keep me from sleeping,” she said between desperate sobs.

“What kind of government is this which can’t protect their own people from unnecessary accidents? And after the accident, they’re not able to find the victims,” Suwarni, who uses only one name, told AP.

Mobile phone video released earlier in the week by the National Disaster Mitigation Agency showed the crew of another ferry attempting to rescue people struggling in the waters shortly after the sinking but being hampered by bad weather and rough waters.

Lake Toba is the largest lake in Indonesia, and sits about 900 metres above sea level. Its cool climate and scenery make it a popular tourist destination, especially during the current Eid holiday season.

Ferry tragedies are common in Indonesia, an archipelago of more than 17,000 islands, with weak enforcement of safety regulations often to blame.