The Latest on Europe's response to the migrant crisis (all times local):

1:30 p.m.

Serbian police say they have found 56 migrants hidden in two vans in eastern Serbia and detained four suspected smugglers.

Police said Thursday 33 migrants were in a van traveling on a regional road in the area near the border with Bulgaria. The remaining 23 migrants were found in the eastern town of Bor.

Migrants have been turning to smugglers to help them reach wealthy European Union nations after the refugee corridor through the Balkans closed in March.

Many travel from Turkey to Bulgaria and then on to Serbia from where they hope to reach EU-member states Hungary or Croatia.

European and Balkan countries have sought to control the influx after more than one million people came last year.

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12:50 p.m.

Greece's coast guard says it rescued about 60 migrants or refugees from a sailboat which ran aground off the coast of the eastern Aegean island of Lesbos, and all passengers were being taken to the island.

The coast guard said the vessel ran aground Thursday south-southwest of Lesbos. Two fishing boats in the area were assisting two coast guard patrol boats.

The number of migrants and refugees reaching Greek islands from the nearby Turkish coast has fallen dramatically in recent months, from hundreds or even thousands daily to none or a few dozen, following a European Union-Turkey deal under which those arriving on or after March 20 face being returned to Turkey unless they successfully apply for asylum in Greece.