ATHENS, Greece (AP) — Greek judicial authorities said Thursday they are investigating the deadly sinking of a migrant boat that was being towed by a coast guard vessel, as officials denied survivors' claims that officers badly mishandled the operation.

The small fishing boat crammed with 28 people had entered Greece illegally from Turkey. The Coast Guard said it was towing the boat to the small Aegean Sea island of Farmakonissi when it capsized and sank Monday leaving two people dead and another 10 — mostly children — missing and feared drowned.

Survivors who arrived in Athens claimed Thursday the boat was being led at speed to nearby Turkish waters to be abandoned. They said Coast Guard crew ignored their pleas to take the women and children on their boat before the accident, and then allegedly stood by as passengers struggled in rough seas.

Greece is a major transit point for illegal immigration into the European Union, and the country has promised to make the issue a priority during its current six-month presidency of the 28-nation bloc.

Merchant Marine Minister Miltiadis Varvitsiotis and Coast Guard officials rejected the survivors' accounts.

"It is not at all true that the vessel was being towed at high speed toward Turkey," Varvitsiotis said. "That is clear from the vessels' coordinates, which we have at our disposal and that anyone who wants can see."

A Coast Guard statement said the crew made "huge efforts" to rescue the immigrants, who were Afghan and Syrian, while also fighting a fire in one of the patrol boat's engines caused by the strain of towing the fishing boat through high waves. It said weather conditions would have endangered any attempt to transfer the migrants to the launch at sea.

International rights groups have urged a full investigation, while Nils Muiznieks, the Council of Europe Commissioner for Human Rights, said Wednesday that the incident "appears to be a case of a failed collective expulsion."

The head of the United Nations refugee agency office in Athens said survivors told a UNHCR official that some of the Coast Guard crew were saying "back to Turkey" and swearing at them in English.

"They said that when the boat capsized they were not thrown ropes or lifejackets but had to swim to the patrol boat, and some said that as they were trying to get up they were hindered," Giorgos Tsarbopoulos said.

"There are clearly two different accounts, which is why we are asking for an in-depth investigation," he said. "I don't know where the truth lies, but what (the survivors) were saying is very serious."

The 16 survivors are being cared for in Athens by an NGO and municipal officials, and given psychological and legal assistance.

"Their main demand now is to have their children's bodies recovered," Tsarbopoulos said. "It seems that they were trapped inside the (fishing boat)."