Dozens of men, women and children from Ethiopia died in the cold waters of Lake Malawi on Monday night. They were on an overcrowded boat that sank with 60 passengers onboard. All are feared dead, and 47 bodies have been found so far.

The dead are presumed to have been illegal immigrants from Ethiopia, and were most likely en route to South Africa. Bodies are being interred in a mass grave since the remains have decomposed.

Davie Chingwalu, Malawi police spokesman, told Agence France-Presse Thursday the search for bodies and possible survivors continues.

Also in progress is an investigation into the human trafficking operation that was behind the tragedy.

We believe the boat capsized due to overloading, and three Malawians have been arrested for aiding the operation with unknown Tanzanians, said Chingwalu.

The Lake Malawi area sees hundreds of illegal migrants crossing its waters every year, according to Al Jazeera. Most come from Ethiopia and Somalia, and are often fleeing poverty, violence, or both. South Africa is the continent's largest economy, and many hope to find a better life there. But first, they must make a dangerous -- and usually illegal -- journey down along the eastern coastal nations of Africa.

Malawi has become a key stopping point along the way, which has contributed to the growth of human trafficking groups. Lake Malawi is used as an alternative to land routes, since roads are often blocked by police.