Security forces and three trucks of riot police blocked off roads around the scarred building compound in Yangon, which encompasses a mosque, a school and a dormitory. There were no reports of violence, but around 200 Muslim residents gathered uneasily nearby, many expressing suspicions the fire had been set intentionally.
Myanmar has been on edge after sectarian unrest between Buddhists and Muslims erupted in the central city of Meikhtila in March, killing dozens of people and displacing more than 12,000. The violence, which has largely targeted Muslims, has since spread to several other towns where extremist Buddhist mobs have torched or ransacked mosques and Muslim-owned property.
Police officer Thet Lwin said about 75 children lived in the mosque compound in eastern Yangon, and most escaped safely by running out of a door police knocked open. Other doors appeared to have been locked, but it was not immediately clear why.
Security bars blocked most of the white building's windows, which were marked by black smoke in the late morning, hours after firefighters put out the flames. The building had burned from the inside.
Mosque member Soe Myint said most of the children, who had been sent to the religious boarding school by their parents, were sleeping on the ground floor when the blaze began and were able to flee.
But 16 of them were sleeping in a small loft on the first floor and were trapped when the ladder that led to the loft caught fire. Three boys jumped to safety, he said, and the rest died.
Thet Lwin, the policeman who was at the scene before dawn, said the fire was triggered by an electrical short "and not due to any criminal activity."
Every time he mentioned the word "electrical short," though, angry Muslims shouted and began banging on vehicles with their fists.
He also appealed on journalists to help. "We need the media's support in Yangon. Please don't report that there is conflict in Yangon. We're here to stop conflict," he said.
Zaw Min Htun, a member of a local Muslim youth organization, said he raced to the mosque early Tuesday after hearing it was on fire.
"Muslims are very angry," he said, calling on authorities to investigate what happened. "The children are innocent. ... Someone burned the mosque."
Zaw Min Htun said he saw no burned wires inside the mosque and said the building's fuse box was in good condition.
The recent upsurge in sectarian unrest in Myanmar has cast a shadow over President Thein Sein's administration as it struggles to make democratic changes after a half-century of military rule. His government has warned the violence could threaten the reform process.
Hundreds of people were killed last year and more than 100,000 made homeless in sectarian violence in western Myanmar between ethnic Rakhine Buddhists and Muslim Rohingyas. On March 20, unrest hit the central town of Meikhtila for several days and then spread to several villages farther south, near the capital Naypyitaw.
The violence had already spooked people in Yangon, where late last month false rumours swirled of mosque burnings and authorities told some businessmen to shutter their shops as a precautionary measure. Yangon is about 550 kilometres (340 miles) south of Meikhtila.