A fire engulfed a mosque housing Muslim schoolchildren in Myanmar’s largest city Tuesday, April 2, killing at least 13, The Associated Press reported.

Authorities, anxious over sectarian violence that has shaken the nation, quickly blamed the blaze on an accidental electrical short.

Security forces and three trucks of riot police blocked off roads around the scarred, two-story building compound in eastern Yangon which encompasses a mosque, a Muslim 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.

Mosque member Soe Myint said most of the children were sleeping on the ground floor when the blaze began and they were able to flee to safety.

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.

Police officer Thet Lwin, who was at the scene before dawn, said the fire was triggered by an electrical short “and not due to any criminal activity.”