The report by an investigation commission appointed by President Thein Sein and chaired by opposition leader Aung San Suu Kyi was released Monday, more than three months after the incident at the Letpadaung copper mine in northwestern Myanmar. It was the biggest use of force against protesters in Myanmar since Thein Sein's reformist government took office in March 2011.
Protesters say the joint venture between China's Wan Bao mining company and a Myanmar military conglomerate causes environmental, social and health problems. They want it halted and are demanding punishment of those who hurt peaceful protesters.
The findings are likely to disappoint opponents of the project and could reignite demonstrations.
Authorities had said they used water cannon, tear gas and smoke grenades to break up the 11-day occupation of the mine last November, but protesters said burns were caused by incendiary devices and at the time they described "fire balls" being shot at them during the nighttime raid on their encampment.
A separate, independent report released last month by a lawyers network and an international human rights group said police dispersed the protesters by using white phosphorous, an incendiary agent generally used in war to create smoke screens.
Monday's report did not specifically mention white phosphorus, saying only that smoke bombs containing phosphorous were used. The report said the smoke bombs do not generally create a flame but the phosphorus in them can sometimes burn flammable materials within an 8-meter radius.
Senior police told the commission that they used the same smoke bombs during monk-led protests in 2007, demonstrations known as Saffron revolution, and they didn't cause any burns.
The commission faulted the police force for failing to understand how the smoke bombs worked and it recommended police receive riot-control training.
Most disappointing for those who oppose the mine, the report said the project "should not be unilaterally stopped." While acknowledging the mine lacked strong environmental protection measures and would not create more jobs for local people, the report said that scrapping the mine could create tension with China and could discourage badly needed future foreign investment.