The UN Refugee Agency (UNHCR) has sent a team to Greece to investigate reports of a major shipwreck in the Mediterranean, UNHCR spokeswoman Ariane Rummery said Tuesday in Geneva.
Witnesses and survivors said Monday that a vessel carrying up to 500 migrants capsized, according to interviews conducted by broadcaster Voice of America.
No government authority or UN agency has been able to corroborate these accounts.
The UNHCR team was sent to the Greek city Kalamata, where the local port authority has confirmed the rescue of 41 people from a wooden boat.
Rummery noted, however, that "there is no official confirmation from the Greek authorities of a relation between the survivors and a larger incident."
"We cannot confirm anything until we have a direct testimony or something from official authorities," said Flavio Di Giacomo, spokesman for the aid and advocacy group International Organization for Migration (IOM) in Rome.
According to reports that have surfaced so far, a boat sailed out of Egypt and met a smaller boat in the middle of the sea that had departed from Tobruk in Libya, Di Giacomo said.
Migrants from the Libyan boat were reportedly moved to the Egyptian boat at sea.
If the vessel really capsized and caused hundreds of deaths, bodies may start washing ashore in Libya in the coming hours, the IOM spokesman told dpa.
Somali government sources have said that there could be up to 200 Somalis among those who are feared dead.
Authorities of the east African country were trying to gather information through their embassies in Italy and Egypt, Somalia's Foreign Minister Abdisalam Omar Hadliye said on state-run radio Mogadishu on Tuesday.
Excluding the possible new shipwreck, 737 migrants and refugees have died so far this year as they tried to cross the Mediterranean to reach southern Europe, according to IOM.