Rescuers continued to search the waters off Spain's El Hierro island on Monday, in the faint hope of finding some of the 48 people reported missing after Saturday's sinking of a boat carrying at least 84 migrants.

Emergency and rescue services said soon after the sinking, which happened in windy conditions and poor visibility about 6.5 kilometers east of the Atlantic Ocean island, that nine people were known to have died in the incident.

Rescuers had responded to an emergency call from the wooden vessel and managed to save 27 people, who they took to a Red Cross field hospital at the port of La Restinga.

Three patrol boats and three helicopters continued to look for survivors on Sunday, although the Spanish coastguard said the possibility of finding more people alive in the water was becoming less likely by the hour.

"Unfortunately, we presume the worst," Candelaria Delgado, a spokeswoman for the Canary Islands government, told Reuters. "The search goes on but it seems that the chances of finding someone alive are slim."

She said many of those who were saved had been suffering from hypothermia and dehydration.

Anselmo Pestana, head of the Canary Islands prefecture, told reporters it looked as if the people onboard the boat, who were from Mali, Mauritania, and Senegal, had not eaten or drunk water for two or three days.

The Canary Island's regional president, Fernando Clavijo, told journalists the 48 missing people were "presumed dead" and that the bodies of many of them would likely be washed ashore in the coming days.

The tragedy off the tiny island that is part of the Canary Islands archipelago could end up being the worst such incident in the region during the past 30 years, officials said.

The boat that went down had set off from Nouadhibou, Mauritania, 800 kilometers away and had capsized as rescuers arrived to take people to safety. The coastguard said the boat had overturned when those on board all rushed to one side as the first rescue vessel arrived.

Some government sources said the boat could have been carrying as many as 90 people and that more than 48 people could be missing.

Officials said the migrants on board had hoped to make their way to the European Union mainland after arriving in the Spanish island and claiming asylum.

The Canary Islands have become a popular destination for people fleeing poverty and conflicts in Africa and the number of boat crossings had increased by 154 percent between January and July, officials said.

The European Union's border agency, Frontex, said 21,620 people are known to have arrived in the Canary Islands by boat to claim asylum during the first seven months of the year.