At least 32 people have died off the coast of southern Greece after a fishing boat carrying dozens of migrants capsized and sank, authorities said Wednesday.

A large search and rescue operation was launched in the area. Authorities said 104 people have been rescued so far following the nighttime incident some 75 kilometers (46 miles) southwest of Greece's southern Peloponnese region.

Also Read: At least 39 migrants dead in bus crash in Panama

Four of the survivors were hospitalized with symptoms of hypothermia. It was unclear how many passengers might remain missing at sea after the 32 bodies were recovered, the Greek coast guard said.

Six coast guard vessels, a navy frigate, a military transport plane, an air force helicopter, several private vessels and a drone from the European Union border protection agency, Frontex, were taking part in the ongoing search.

Also Read: Migrant boat breaks up off Italian coast, killing nearly 60

The Italy-bound boat is believed to have sailed from the Tobruk area in eastern Libya. The Italian coast guard first alerted Greek authorities and Frontex about the approaching vessel on Tuesday.

Smugglers are increasingly taking larger boats into international waters off the Greek mainland to try to avoid local coast guard patrols.

Also Read: Death toll from Greece train crash rises to 57

On Sunday, 90 migrants on a U.S.-flagged yacht were rescued in the area after they made a distress call.

Separately Wednesday, a yacht with 81 migrants on board was towed to a port on the south coast of Greece's island of Crete after authorities received a distress call.

Also Read: Greece: 3 dead after boat with migrants hits rocks