Sinking of MV Sinar Bangun

The first vessel that managed to reach the site of the disaster was the MV Sumut II RORO vessel. It managed to rescue and evacuate 3 people from the site. Fifteen minutes later, MV Sumut I and MV Sinta Dame II arrived at the site. MV Sumut I rescued 14 survivors and the latter managed to evacuate 1 survivor and 1 dead body. At 17:40 local time, the Indonesian National Search and Rescue Agency was informed about the disaster.[11] A joint search and rescue team was assembled and deployed in the area, consisting of the National Search and Rescue Agency, the National Armed Forces, regional and local government officials, the Agency for Meteorology, Climatology and Geophysics, and the regional Disaster Management Board. The site of the sinking is two nautical miles (3.7 km; 2.3 mi) from the harbour. Eighteen people were found to have survived the sinking.[21] The first victim of the disaster was identified as Tri Suci Wulandari, a student from Aceh Tamiang, Aceh.[22] Helicopters and ferries were deployed by authorities. The survivors were transported to Simarmata Community Health Center, Hadrinus Sinaga Regional Hospital and Dolok Padarmean Community Health Center.[23]

Search and Rescue Mission Coordinator divided the joint search and rescue team into 2 groups. Officials stated that 350 personnel were deployed to assist the search and rescue operation.[24] The rescue operation was hampered by bad weather[25] and lack of equipment. Personnel from Jakarta were called. Personal belongings were retrieved from the water; however, neither victims nor survivors were found.[26] The search and rescue operation was called off. On late evening of 19 June, a C-130 Hercules carrying multiple personnel and advanced equipment arrived at Silangit Airport.[27]

At least seven ships were deployed by the command center.[28] The search area was widened to 3.6 square kilometres (1.4 sq mi).[29] Divers were dispatched to Lake Toba. By the evening, search and rescue recovered more bodies.[30] Authorities stated that the other bodies were most likely trapped inside the wreckage of the ferry.[31]

Officials from the National Search and Rescue Agency stated that the rescue operation would be conducted for seven days. Minister of Transportation Budi Karya Sumadi stated that the search and rescue operation would be extended to ten days if necessary.[32]

Members of the Indonesian National Search and Rescue Agency lowered an ROV to search the wreckage of MV Sinar Bangun

The search area was widened to 15 square kilometres (5.8 sq mi) to the east, as projection made by the Indonesian BMKG predicted that the current would carry the passengers and crews to the east. Ten boats were deployed to the search area.[11]

Lake Toba is known to be up to 500 metres (1,600 ft) deep in many places; however, depth traces by the search team indicated depths of up to 1,600 metres (5,200 ft), which is far beyond the 350-metre (1,150 ft) maximum working depth of the deployed Remote Observation Vehicle, and no traces of the ship were found. Separate sonar tools, effective up to 600 metres (2,000 ft), also showed the lake was deeper than 600 metres. As a result, a 2,000-metre (6,600 ft) sonar tool was ordered to be sent to the area.[33]

The search area was widened again to 25 square kilometres (9.7 sq mi) to the east. A helicopter was deployed to assist the search and rescue. Volunteers also searched for bodies or survivors on the shore. The Indonesian Navy was deployed to conduct an underwater sonar scan.[11]

Officials decided to widen the search area for 10 square kilometres (3.9 sq mi) to the east. On the evening, a meeting was held between authorities and family members to discuss whether the search and rescue effort should be continued or not. Both parties agreed to extend the search and rescue period to another 3 days.

The Indonesian Search and Rescue Agency announced that their personnel had captured an object in their sonar image. The object was located at a depth of 450 metres (1,480 ft). The object was suspected to be the wreckage of the ferry. Salvage operation was conducted. Later in the evening, the Head of the Indonesian Search and Rescue Agency, Muhammad Syaugi, stated that an ROV spotted bodies and motorcycles in the surrounding area. Photos of the submerged motorcycles and the dead bodies were shown to the media.[34][35]

The government announced that the search would be stopped on 3 July. The reason is that the agency had found difficulties because Lake Toba's depth is more than 450-metre (1,480 ft) while at this time the agency only has the ability to search up to 200-metre (660 ft). The victims' families had said that they are already letting go of their relatives.[36]

On 19 November 2018, more than 5 months after the disaster, the Indonesian National Transportation Safety Committee published the final report of the investigation. They concluded that the disaster was caused by overloading. The first deck and the second deck of the ferry was overly loaded with passengers. It was so crowded that dozens of passengers had to stand up while the ferry was en route to Simalungun. However, the presence of the third deck, which was located on top of the ferry and was used as a selfie spot, was a major factor of the capsizing. During the disaster, the third deck was heavily crowded. Calculation made by the NTSC revealed that due to this, the ferry could easily capsize as the righting moment of the ferry was small. While the ferry was en route to Simalungun, the weather deteriorated and high waves were produced. The high waves and the heavy wind which was blowing to the side of the ferry then caused the ferry to capsize.[11]

Another factor contributing to the capsizing is the use of steel on the structure of the ferry. Most parts of the ferry were made of steel. Since steel is heavier than wood and since it was used for the third deck and on some parts of the ferry, the ferry becomes more unstable.[11]

Investigators noted that the ferry was not equipped with sufficient life jackets. However, even if the ferry had been equipped with sufficient life jackets, NTSC stated that no one would have been able to wear them as the capsizing happened so quickly. Investigators noted that the ferry also didn't have sufficient emergency doors (there was only one emergency door on board) and that the vehicles were placed improperly in the ferry. The vehicles blocked the doors on the ferry, causing people to be trapped.[11]

Further investigation revealed that the Captain was never trained properly. He also didn't know how to deal with an emergency. Deviation from regulations and insufficient supervision from local officials also contributed to the poor quality of the crew.[11]

The report also criticized the actions of the crews of MV Sumut II who, according to the report, didn't make a serious effort to save the survivors. Examination on the video of the rescue operation showed that the crew of MV Sumut II had only managed to save three survivors even though the ship was still able to carry more survivors. At the time, dozens of survivors were still floating near the ship. The remaining survivors were later abandoned until the MV Sumut I and MV Sinta Dame II arrived at the site. Investigators noted that during this time, the number of survivors had decreased significantly as several survivors had drowned due to exhaustion.[11]