An investigation into the government's response to a November protest at the Letpadaung copper mine found authorities used white phosphorus on demonstrators. The report was conducted by Justice Trust in the United States and the Lawyers Network in Myanmar.
Justice Trust Director Roger Normand said from Yangon that Myanmar forces were excessive with their response.
"It is unheard of for police to use incendiary military munitions against peaceful protesters during a law enforcement operation," he was quoted by The Irrawaddy, a Myanmar newspaper published in Thailand, as saying. "This raises questions of senior-level command responsibility for resulting crimes and violations of people's constitutional and human rights."
Irrawaddy reports that pro-democracy leader Aung San Suu Kyi missed a Jan. 31 deadline to publish an official inquiry into the incident.
World governments have eased diplomatic pressure on Myanmar follow political reforms that began with general elections in 2010. Human rights and internal conflict has clouded government developments, however.
The copper mine is owned by the Myanmar military and the Chinese. Villagers there said they were forced from their land to make way for development.