Coast guard officials said yesterday that they were on the trail of a Ukrainian national who worked with Turkish smugglers to bring dozens of would-be migrants into Greece. Authorities said they are acting on information gleaned from an investigation that started last July with the arrest of two Ukrainians and two Iraqis after a boatload of 48 Pakistanis reached the coastal resort of Agiokambos, central Greece. The boat carrying the migrants, the Ukrainian-flagged Adria, is believed to belong to Sergey Andyonov. He is believed to have organized countless transfers of migrants aboard his boat, working with a well-organized ring in Turkey. The Iraqis are believed to have handled things on the Greek side. According to sources Andyonov had been running his operation from the Turkish coastal resort of Ayvalik.