A migrant boat has capsized off the Libyan coast, leaving at least 35 people dead or presumed dead, the U.N. migration agency said Saturday.

The shipwreck took place Friday off the western Libyan city of Sabratha, a major launching point for the mainly African migrants making the dangerous voyage across the Mediterranean Sea, said the International Organization for Migration.

The IOM said the bodies of six migrants were pulled out, while 29 others were missing and presumed dead. It was not immediately clear what caused the wooden boat to capsize.

The tragedy was the latest to involve migrants departing from North Africa to seek a better life in Europe. This past week alone, at least 53 migrants were reported dead or presumed dead off Libya, according to the IOM.

“Dedicated search and rescue capacity and a safe disembarkation mechanism are urgently needed to prevent further deaths and suffering,” the IOM said.

Investigators commissioned by the United Nations’ top human rights body found evidence of possible crimes against humanity committed in Libya against migrants detained in government-run prisons and at the hands of human traffickers.

Earlier this month, more than 90 people in an overcrowded boat drowned in the Mediterranean Sea, days after they left Libya, according to the Doctors Without Borders aid group.

Migrants regularly try to cross the Mediterranean from Libya in a desperate attempt to reach European shores. The country has emerged as the dominant transit point for migrants fleeing war and poverty in Africa and the Middle East.

Human traffickers in recent years have benefited from the chaos in Libya, smuggling in migrants across the oil-rich country’s lengthy borders with six nations. The migrants are then typically packed into ill-equipped rubber boats and set off on risky sea voyages.

At least 476 migrants died along the central Mediterranean route between Jan. 1 and April 11, according to the IOM.

Once back in Libya, the migrants are typically taken to government-run detention centers rife with abuse and ill-treatment.