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MADRID — Dozens of migrants were feared dead after waiting for more than 36 hours to be rescued from a semi-sunken boat in waters off Morocco, according to a Spanish nonprofit group.

The Moroccan Interior Ministry said Tuesday 11 bodies were recovered and the boat's teenage skipper had been detained.

The migrants continuously pleaded for help from Spanish and Moroccan authorities for at least 12 hours Sunday before their cellphones lost power, Walking Borders founder Helena Maleno told the Associated Press.

Maleno said she alerted Spain's maritime rescue service about the sinking dinghy and its approximate location and that 26 survivors, all from sub-Saharan African countries, were brought ashore 1½ days later in the northern Moroccan town of Nador.

A spokeswoman for Spain's rescue service said the vessel was within Morocco's jurisdictional waters in the western Mediterranean Sea and the agency repeatedly offered to help with a search-and-rescue operation, but received no response from Morocco.

"The dinghy was in an area very close to Morocco, not far from the beach," said the spokeswoman, who was not authorized to be named in media reports.

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The Moroccan Interior Ministry said late Tuesday that the bodies of 11 African migrants had been found off Nador. A ministry statement said 31 others were rescued from the boat.

Moroccan authorities did not address Maleno's allegation of a holdup in the rescue operation.

The U.N's International Organization for Migration said it couldn't independently confirm Maleno's account. IOM spokesman Joel Millman said Walking Borders was a "reliable" source of information in the part of the world it serves.

Maleno said she came up with the possible death count of 32 adults and two children from survivor accounts, including from the mother of one of the children feared dead.

Morocco and Spain cooperate closely at the security level to crack down on trafficking networks but they are not doing enough to save lives at sea, according to Manelo.

"There was a lack of coordination to rescue them, and they were left to die slowly," Maleno said.

The bodies of 11 African migrants were found off Nador, Morocco. Bing Maps

She described the survivors as being in deep shock.

"They have spent many hours watching people die and many hours in the water," she added. "This is not the same as a fast-paced wreck; it has been a real torture for them."

In an incident last month, the Moroccan navy fired at a speedboat carrying migrants after it refused to stop, killing a young woman and injuring three other people.

Commenting on that incident, Morocco's Prime Minister Saad Eddine El Othmani said the navy had not seen the migrants because they were hiding in the boat.

According to the International Organization for Migration, more than 36,600 migrants arrived in Spain by sea during the first nine months of the year, a jump in the number from previous years that has put a strain on public services.

During the same period, more than 360 migrants were reported to have died in the waters separating Spain from the African coast, doubling the figure from the first three quarters of 2017.

More than 1,700 have died on the various Mediterranean Sea routes altogether.