Authorities in Indonesia say 192 people could be missing after a ferry sank in a large volcanic lake on Sumatra Island in the country’s west.

The latest estimate from rescue officials on Wednesday afternoon is three times the original toll estimated by government officials after the boat capsized on Lake Toba on Monday. It is still unclear how many people were on board the vessel.

The traditional wooden boat may have been operating illegally with no manifest or passenger tickets, sparking confusion and a string of changing official passenger estimates, AFP reported.

Indonesia’s disaster agency originally said some 80 people along with dozens of motorcycles were on the overloaded, 43-passenger capacity vessel when it overturned and sank. So far, four bodies have been found and another 18 people rescued, according to the agency.

Authorities based the figures on reports from families whose missing relatives may have been on the doomed vessel, but their accounts are difficult to verify. If confirmed, it would be one of Indonesia’s deadliest maritime disasters.

“Many people got on the boat without a ticket so it’s unclear how many were on board,” Muhammad Syaugi, the head of the search and rescue agency, told AFP.

Later at a press conference, Syaugi added: “There are many people who have reported their relatives missing, but whether they were on the boat or not we don’t know.”

The search has now turned to recovering bodies, including those that may still be trapped inside the sunken boat.