Myanmar may have freed all remaining political prisoners: opposition YANGON (Reuters) - Myanmar may have released all of its remaining political prisoners in an amnesty for 514 detainees on Monday, the main opposition party said, just over a week ahead of a rare visit by its reformist president to the United States. "We're optimistic that these are the remaining political prisoners," said Naing Naing, a central executive committee member of Aung San Suu Kyi's National League for Democracy party. He said he understood 424 political detainees were freed in the amnesty. That figure would exclude inmates who were former military intelligence officials purged under the former junta. President Thein Sein, whose government has released more than 650 political prisoners since taking office in March last year, was due to head to the United States on September 24, where he will address the United Nations General Assembly in New York for the first time as president. Reporting by Aung Hla Tun; Writing by Martin Petty; Editing by Jeremy Laurence