LAS PALMAS DE GRAN CANARIA, Spain (AP) — Spanish authorities on Wednesday located a boat near the Canary Islands with dead migrants on board, some floating in sea water the vessel took on.

The Spanish Maritime Rescue Service said there were around 10 bodies on the boat.

The shipwreck was spotted by a plane as it searched for a missing boat that had left Mauritania on Aug. 15 with around 40 people on board and was believed to be heading to the Spanish islands off northwest Africa.

Two Spanish rescue service vessels reached the shipwreck about 150 kilometers (85 miles) south of the island of Gran Canaria. They were waiting for Guardia Civil police officers to arrive and remove the bodies, providing an exact number of deaths.

The route from western Africa to Spain’s Canary Islands is notoriously dangerous but in recent times has increasingly attracted migrants wanting to reach European soil, as authorities on Mediterranean routes have cracked down on migrant boats.

Since August last year, at least 357 migrants have died trying to reach the Canary islands, according to the U.N. migration agency.

So far this year, more than 3,500 migrants have arrived in the archipelago, the Spanish Interior Ministry says.

In the Mediterranean Sea, meanwhile, Spanish authorities on Wednesday reported 99 migrants had been rescued at sea, with another 23 arriving in Mallorca under their own steam.