TIGARAS, Indonesia -- Indonesia on Tuesday ended a search of one of the world's deepest lakes for the bodies of dozens of victims of a ferry sinking two weeks ago.

The day, dreaded by families of the missing, was marked with prayers and a groundbreaking ceremony for a monument that will be inscribed with the names of victims. Weeping relatives cast flowers into the lake.

The wooden ferry, five times above its passenger limit and also carrying dozens of motorcycles, sank in the volcanic crater lake on Sumatra in rough weather on June 18.

The full scale of the tragedy took days to unfold as the boat didn't have a passenger manifest. Officials at one point said more than 190 people were missing. Their official toll Tuesday was 21 survivors, including the boat's captain, three bodies found and 164 people missing, presumed drowned.

Sonar has pinpointed the ferry at a depth of 450 metres (1,476 feet). A remotely operated underwater vehicle last week captured images of bodies and motorcycles on the lake bed. But Indonesia lacks the sophisticated equipment needed to seriously attempt a salvage effort. Officials had said many bodies were likely inside the boat.

"To lift from a depth of 450 metres at the bottom of the lake is not an easy task because it requires advanced technology which we do not have," Indonesia's maritime minister, Luhut Binsar Panjaitan, told reporters. "Even if it can be done, it will take time and involve huge risks."

The head of North Sumatra province's Search and Rescue agency, Budiawan, who uses one name, said the decision to call off the search was made after "intense" discussions with the families of victims.

"After all this ended, we'll all go home even though we are disappointed," said Murni Sihombing, a grieving relative. "We had hoped that there would be help from the international community."

Police in Medan, the capital of North Sumatra province, said they're finalizing criminal charges against five people, including the captain, and four transportation officials.

"They knew the capacity of the ferry Sinar Bangun was only about 40," North Sumatra police chief Paulus Waterpau said Monday. "Moreover, as a wooden boat, it should not have been allowed to carry motorcycles."

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

On Tuesday, at least 12 people were killed and a frantic rescue operation was underway off the Indonesian island of Sulawesi for dozens of passengers of a sinking passenger ferry run aground by its captain in a desperate bid to save lives.

The Lake Toba sinking was the worst in about a decade.

Kotarumalos reported from Jakarta, Indonesia