MADRID (AP) — Spanish rescue services have located 1,300 migrants in four days in the Atlantic Ocean and transferred them to the southern Canary Islands, further straining local emergency response capabilities as makeshift military camps for the newcomers were being readied.

The latest to arrive were 27 men from northern Africa who were picked up from the high seas early Monday, Spain’s Maritime Rescue Service told The Associated Press, adding to the 1,275 people found from Friday to Sunday aboard 42 boats.

More than half of the 16,000 migrants who arrived this year in the Spanish islands off northwest Africa did so in the last four weeks, a sharp influx worrying international and non-profit organizations.

That’s compared to around 1,500 arrivals recorded last year in the archipelago, better known for its vacation resorts popular among northern Europeans.

Officials from the U.N. refugee and migration agencies were visiting the islands this week to assess the crisis, which the IOM and UNCHR agencies said has been fueled by people fleeing violence in the Sahel region or the Ivory Coast, extreme poverty, climate change and the coronavirus pandemic.

“The COVID-19 context poses an additional challenge, taking into account the profiles and special vulnerability of some newcomers, including women, girls and boys, some unaccompanied, victims of trafficking or people in need of international protection,” a joint statement from the two agencies said Monday.

The government has halted all but a few transfers of the migrants from the archipelago to mainland Spain, a decision that high-ranking officials from the Foreign Ministry have justified in private as part of the government’s “zero tolerance” toward migrants who don’t qualify for legal work or asylum.

But that has led to a concentration of people on some of the islands, especially at a dock on the southwestern coast of Gran Canaria island, where a steady number of 2,000 people have been spending night after night on hard concrete and under Red Cross tents.

The Spanish government says it plans to increase aid for Africa while speeding up deportations of those who don’t meet the criteria to stay in Europe and funding police operations against people traffickers in Morocco, Mauritania and Senegal, the northwestern African countries that are the main points of departure for migrants bound for the Canaries.

Several makeshift military camps have also been prepared to host migrants who are crammed at the Arguineguin dock, and Interior Minister Fernando Grande-Marlaska said Monday that the transfers would be initiated “soon.”

Interviewed on Antena 3 Television, Grande-Marlaska said that the makeshift camps were only for the first 72 hours when the migrants are in police custody while deciding whether they meet the criteria to stay, and rejected the idea of turning the Canary Islands into Europe’s “new Lesbos,” in reference to the Greek island infamously known for its refugee camps.

The new migrant focus on the perilous Canary Islands route, first seen in 2006, has come as authorities crack down on previously popular passages across the Mediterranean Sea from North Africa to European Union countries.

With at least 493 deaths recorded so far this year, up from 210 in all of 2019, the route to the Spanish archipelago has seen proportionally more deaths per every arrival than the Central Mediterranean journey from Libya to Italy or Malta. The perilous trip from far-flung Senegal can take up to two weeks in rough waters.