Rescue crews in Greece were searching on Wednesday for migrants who sent out an emergency call from the Greek-Turkish border late on Tuesday, the Greek fire brigade said.
State television said authorities believed about 15 people went missing as they tried to cross the swollen and fast-flowing Evros river which divides Greece from Turkey in the far northeast.
Firefighters were responding to a call to the European Union-wide emergency number 112 but had not found anyone yet, a fire brigade spokeswoman said.
More migrants and refugees are attempting to cross into Greece through its land border with Turkey since a 2016 EU deal with Ankara all but closed the sea route to Greek islands which almost a million people took in 2015.
The Evros crossing is dangerous, and a woman and two children drowned in the river last month. At least 19 people drowned in 2010, according to the United Nations refugee agency.