Greece is sending a navy frigate and a helicopter to locate a cargo ship believed to be carrying about 600 migrants in the northern Ionian Sea after authorities received a distress call from someone on board, The Associated Press reported. The ship, the Moldovan-flagged Blue Sky M, was sailing in poor weather near the tiny island of Othonoi, northwest of Corfu. Authorities said the distress call had come from one of the passengers on board the ship. The incident comes two days after a Greek passenger ferry with more than 400 people on board caught fire in the same area. At least 10 people died in that incident.