At least 300 people who were traveling on three migrant boats from Senegal to Spain’s Canary Islands have disappeared, migrant aid group Walking Borders said on Sunday, according to Reuters. 

Two boats, one carrying about 65 people and the other with between 50 and 60 on board, have been missing for 15 days since they left Senegal to try to reach Spain, Helena Maleno of Walking Borders told Reuters.

A third boat left Senegal on June 27 with about 200 people aboard.

The families of those on board have not heard from them since they left, Maleno said.

All three boats left Kafountine in the south of Senegal, which is about 1,700 kilometers from Tenerife, one of the Canary Islands.

“The families are very worried. There are about 300 people from the same area of Senegal. They have left because of the instability in Senegal,” Maleno said.

The Canary Islands off the coast of West Africa have become the main destination for migrants trying to reach Spain, with a much smaller number also seeking to cross the Mediterranean Sea to the Spanish mainland. Summer is the busiest period for all attempted crossings.