By AYE AYE WINYANGON, Myanmar (AP) â¿¿ Activists in Myanmar demanded punishment Thursday for officials who were responsible for the use of incendiary weapons against peaceful protesters at a copper mine, resulting in serious burns for dozens of people including Buddhist monks. Lawyers and others who investigated the Nov. 29 crackdown at the Letpadaung copper mine in northwestern Myanmar told reporters that President Thein Sein must share responsibility and ensure justice is achieved. Speaking at the launch of a report on the incident, they said police used shells containing white phosphorous, an incendiary munition, to disperse the protesters. White phosphorous can be used legally in some battlefield conditions, but activists say it should not be deployed against civilians. Authorities have acknowledged using tear gas and smoke grenades. The incident involved the biggest use of force against protesters in Myanmar since Thein Sein's reformist government took office in March 2011 after almost five decades of repressive military rule. His administration has been hailed for releasing hundreds of political prisoners and implementing laws allowing public demonstrations and labor strikes. Protesters say the mine project, a joint venture between China's Wan Bao mining company â¿¿ a subsidiary of NORINCO, a weapons manufacturer â¿¿ and the military conglomerate Union of Myanmar Economic Holding Ltd. â¿¿ a military-owned holding company â¿¿ causes environmental, social and health problems, and want it halted. "The use of inherently dangerous military arms to disperse peaceful protesters, apparently by local police during a standard law enforcement procedure, is clearly unlawful and raises issues of liability for those directly involved and for senior responsible levels of command and control in the military and government and for senior executives/military officers at Wan Bao and UMEHL," the report said. It was compiled by Lawyers' Network, an independent association of leading Myanmar lawyers, and Justice Trust, an international group engaged in supporting the rule of law and human rights.