Rescue workers are carrying a dinghy used to rescue 59 migrants and deliver them to Malaga harbor, Spain, May 7, 2019. (Photo: VCG)

Spanish rescue services are searching for at least 20 people missing from a migrant boat, which was found adrift in the Mediterranean after a passenger ferry rescued 27 people still aboard on Wednesday. 

The number of migrants arriving in Europe by sea, already declining steadily since 2015 and it has fallen further this year as the European Union increasingly focuses on border control. 

The migrant boat was reported missing on Tuesday with 49 people on board after setting off from northeastern Morocco, rescue services said.  

A passenger ship found the boat on Wednesday afternoon, rescuing 27 people, six of whom were evacuated by a helicopter. 

Irregular sea arrivals from the Middle East and North Africa have dropped from over 1 million in 2015 to a little over 140,000 people last year, United Nations data show.  

Fewer than 23,000 refugees and migrants have made it across the sea to Europe so far this year. 

This week rights group the Council of Europe said the EU was violating international law with its increasingly restrictive stance on immigration and called on the bloc to step up sea rescues.