Three people died and four are missing after a migrants boat carrying eight people capsized on Tuesday in a river that flows between Turkey and Greece, a spokeswoman for Turkey’s Disaster and Emergency Organisation (AFAD) said. The eighth refugee had made it into Greece, she added.

The boat was travelling along the Maritsa River, in Turkey’s northwestern province of Edirne, when it capsized early on Tuesday, the first aid organisation said. Nearby residents heard screams and informed the local gendarmerie forces.

Searchers recovered three bodies, AFAD said, adding that two of them were children – one around 12 years old and the other around four. The causes of death have not yet been determined.

AFAD was still looking for the four others who were also on the boat but said the cold temperatures and the strong currents in the water was impeding operations.

A 2016 deal between Turkey and the European Union sharply reduced the flow of refugees into the bloc, many of whom had made the short but dangerous sea crossing from Turkey to the Greek islands a few miles offshore.

Overall Mediterranean arrivals to the European Union, including refugees making the longer and more perilous crossing from north Africa to Italy, stood at 172,301 in 2017, down from 362,753 in 2016 and 1,015,078 in 2015, according to U.N. data.