A U.N. visit to Myanmar's troubled Rakhine state was postponed Thursday because of bad weather.
Word of the delay came one day after the U.N. said its representatives would be accompanied by Myanmar government officials in a visit to Rakhine.
The U.N. said the visit had been postponed until next week. Access to the region adjacent to Bangladesh has been strictly controlled by Myanmar's government.
The trip would be the first by U.N. representatives into Rakhine since the beginning of a mass exodus of Rohingya Muslims.
The United Nations said Thursday that more than 500,000 refugees from Myanmar had crossed the border into Bangladesh. The U.N. attributed the higher number to improved counting, not a dramatic increase in arrivals.
Meanwhile, 13 people, including eight children, were killed Thursday when a boat capsized while traveling from Myanmar to Bangladesh. Thirty Rohingya were rescued from the boat, which was carrying 120 people.
"Dozens of others are believed to have perished making similar journeys since the latest crisis in Rakhine state erupted in late August," UNICEF said in a statement. "All told, over a quarter of a million children from Myanmar have now taken refuge in southern Bangladesh in recent weeks."
Violence erupted between Rohingya and Myanmar's military in Rakhine state on August 25, when a group of Rohingya militants attacked dozens of police posts and an army base in what militants said was an effort to protect their ethnic minority from persecution.
About 400 people have been killed in subsequent clashes. Satellite images released by rights group Amnesty International have shown entire Rohingya villages burned.
In Photos: Mass Grave Site in Northern Rakhine State