DIKILI, Turkey (AP) — A first group of migrants were ferried from the Greek islands to Turkey today as part of a controversial European Union plan to curb migration to Europe.

Under heavy security, authorities on the Greek islands of Lesbos and Chios put 202 people on boats bound for Turkey — the first to be sent back as part of the plan, which has drawn strong criticism from human rights advocates.

The first vessel arrived later in the Turkish port of Dikili, where migrants were taken to red-and-white tents for registration and health checks. About a dozen people stood at the port holding a banner that read “Welcome refugees. Turkey is your home.”

A second vessel was expected soon after. Authorities said most of the people in the first batch are Pakistani nationals.

Turkey and the European Union reached a deal last month which stipulates that migrants who reach Greece illegally from Turkey after March 20 will be returned to Turkey unless they qualify for asylum. For every Syrian turned back, a Syrian refugee is to be resettled from Turkey to the EU.

Today was the designated start date for transfers and marks a symbolic, successful benchmark in the agreement, which has been plagued by concerns over human rights and the adequacy of preparations taken in Greece and Turkey. The numbers transferred, however, were smaller than initially forecast.

“All of the migrants returned are from Pakistan except two migrants from Syria who returned voluntarily,” said Giorgos Kyritsis, a spokesman for a government refugee crisis committee.

About 4,000 migrants and refugees have been detained on Greek islands since the agreement came into effect.

A total of 50,000 migrants and refugees are stranded in Greece following EU and Balkan border closures, but only those who arrived after March 20 will be detained for deportation.