ISTANBUL — Some 58 people drowned when a fishing boat carrying migrants promised refuge in Europe by smugglers sank after hitting rocks off the coast of western Turkey, officials said Thursday.

Nine children were among the dead, according to the Dogan News Agency. Several dozen survivors, mostly from Iraq and Syria, swam to shore, only 160 feet away.

Survivors told authorities some people were trapped below the deck of the submerged vessel, and divers launched an operation to try to find them. Ambulances waited at the top of a cliff, but there were no indications anyone else had survived.

The migrants had previously made their way to hotels in the city of Izmir, where smugglers agreed to take them to Britain. Authorities arrested two Turkish suspects in the smuggling operation.

Those who survived were on the deck. It was not immediately clear when the boat sank, but many such vessels carrying migrants make the journey at night.

Each year, thousands try to sail to Greek islands from Turkish soil in rickety boats.

Greece said in July that it was quadrupling the number of guards at its border with Turkey and boosting other defenses, in part because of worries about a potential influx. Some nongovernmental groups say that migrants, deterred by tighter enforcement on the land border, are now turning back to more dangerous sea routes in their effort to start a life elsewhere.