ATHENS, Greece — Greece is sending a navy frigate and a helicopter to locate a cargo ship believed to be carrying hundreds of migrants after authorities received a distress call from someone on board, authorities said. The ship, the Moldovan-flagged Blue Sky M, was sailing in poor weather near the tiny island of Othonoi, northwest of Corfu in the Ionian Sea. A merchant marine ministry official, speaking on condition of anonymity because no official information had been issued, said the distress call came from one of the passengers on board. The ship is believed to be carrying 400-600 migrants.

The incident comes two days after a Greek ferry carrying more than 400 people caught fire in the same area, sparking a rescue operation by Italian and Greek coast guard and military officials. At least 10 people died while more than 400 were rescued from the Norman Atlantic, and authorities were still searching for potential missing passengers. The Greek frigate Navarino, which is heading to locate the cargo ship, had been in the area assisting in the rescue operation for the ferry.

Armed special missions officers of the Greek coast guard set off from Corfu harbor for waters off the Ionian island of Othoni, responding to a distress signal from Moldovan-registered freighter 'Blue Sky M' in the area, in Corfu, Greece, on Dec. 30. MARIA TZORA / EPA

— The Associated Press