At least 60 migrants are presumed dead after a boat disaster off Cape Verde, West Africa, according to the International Organization on Migration (IOM).

A total 101 people were on board the boat at the time, the IOM told CNN on Thursday, with 38 people, including four children, rescued.

Seven people are confirmed dead, and 56 people are missing. Those missing at sea are presumed dead, according to the IOM, making for an estimated death toll of 63.

“We are still unclear about the circumstances of what happened to the boat, but being stranded at sea for this prolonged period of time poses severe risks in addition to drowning,” IOM spokesperson Safa Msehli told CNN, adding that this includes a risk of hypothermia and dehydration.

According to the IOM, the boat departed from the coast of Fass Boye in Senegal on July 10 and was rescued on August 15.

The Cape Verde archipelago consists of 10 islands and is located in the North Atlantic about 570 kilometers (about 350 miles) off the extreme western tip of Africa.

Recently there have been “an increasing number of immigrants arriving” in the archipelago, according to the IOM, which adds that the nation has recently graduated from a lower- to a middle-income country.

It is unclear whether the migrants intended to reach Cape Verde as their final destination, or whether they were heading for the Canary Islands, another archipelago around 1,500 kilometers to the north.

The Canary Islands are part of Spain, and in recent years have become an increasingly popular destination for migrants from West Africa trying to reach Europe.

A total of 9,864 migrants have arrived by boat to the Canary Islands this year through August 15, a 4.7% decline compared with the same period last year, Spain’s interior ministry reported.