A brief announcement on the evening news said the explosion occurred on the Yangon-Mandalay rail line about 25 miles (40 kilometers) north of the capital Naypyitaw and 250 miles (400 kilometers) north of Yangon. The report said the blast blew a hole in the roof of the carriage. It did not mention if any foreigners were hurt.
No one immediately claimed responsibility for the blast and no suspects have been named.
The bombing occurred as a U.S. diplomat was visiting Naypyitaw for talks with the new civilian government, though there was no apparent connection between the events. The visit by Deputy Assistant Secretary of State for East Asian and Pacific Affairs Joseph Y. Yun comes as the U.S. and other countries consider their policies after Myanmar's recent transition from direct military rule to an elected civilian government - but one that critics charge merely fronts for the army.
Bombings are rare but not unknown in Myanmar, where pro-democracy activists and ethnic minority groups are at odds with the military-backed regime. The government usually blames opposition militants for such blasts, but most remain shrouded in mystery.