ATHENS: Four bodies were recovered and 340 people rescued Friday from a sinking migrant boat carrying a 'significant number' of people in the Mediterranean Sea south of the Greek island of Crete, authorities said. The coast guard said the roughly 25-meter (82-foot) vessel, which resembled a large fishing boat, had been carrying an undetermined number of people when it was located Friday half-sunk about 75 nautical miles south of Crete in international waters, and within Egypt's search and rescue area of operation. Greece was sending two patrol vessels, a military airplane and three helicopters, while five passing ships were participating in the rescue operation and one more was on its way. The coast guard said the operation was continuing to locate any potentially missing passengers from the migrant boat. It was not immediately clear where the boat's passengers were from, or where the vessel had set off from or was heading to. 'The information we have on the number of people on board the vessel is still unclear we've heard that there were 400 or 500 people on board, but we cannot confirm that number,' Coast Guard spokesman Nikos Lagadianos said. 'There is a huge rescue effort underway.' It wasn't immediately clear where the survivors will be taken. Authorities in southern Crete said temporary shelter space possibly sports facilities was being sought on the island to house people if they are taken there. Migrant smugglers have opted for more dangerous routes after a March agreement. The short crossing from the Turkish coast to Greek islands was the preferred route for migrants heading to Europe until Balkan countries closed their borders and the European Union reached an agreement with Turkey to stem the flow of people. Under that deal, those arriving on Greek islands from March 20 onwards face deportation back to Turkey unless they successfully apply for asylum in Greece, a financially troubled country few migrants or refugees want to stay in. The deal has led to a dramatic decrease in the number of people arriving on Greek islands from Turkey. The coast guard said it and European border patrol agency Frontex had rescued 164 people in four separate incidents Thursday off the islands of Lesbos and Chios. Before the EU-Turkey deal, thousands would arrive each day. However, the agreement has led refugees and migrants to seek alternative routes, with many attempting the much longer and more dangerous crossing from north Africa towards Italy. Hundreds have died in the past few weeks when overcrowded boats attempting the crossing sank.