Madrid, Spain - Four people were found dead in a boat full of migrants that was rescued overnight off the Canary Islands, Spanish maritime officials said Wednesday.

Lifeguards took 64 survivors, many in poor health, from the vessel found late on Tuesday off the island of El Hierro, Spain's maritime rescue service wrote on X, formerly Twitter.

Two of the migrants were transported by helicopter to a hospital in Tenerife, the largest of the seven islands which make up the archipelago off the northwest coast of Africa, it added.

Another 14 people were taken to hospital on El Hierro, mainly to be treated for hypothermia and dehydration.

Just under 40,000 migrants arrived by boat in the Canaries in 2023 after making the perilous crossing from Africa, an increase of nearly 155 percent over last year and surpassing the record number set in 2006.

A lot of them arrived at El Hierro, the most westerly of Spain's Canary Islands in the Atlantic, overwhelming social services on the tiny island which normally does not receive large numbers of migrants.

The Atlantic migration route to the Canaries, one of the deadliest in the world, is typically used by migrants from sub-Saharan Africa trying to reach Europe.