The US ambassador in Honduras has blamed a fire last month at an overcrowded prison in the Central American country that killed 361 inmates, on official negligence. An investigation by agents from the US Bureau of Alcohol, Tobacco and Firearms (ATF) earlier found that the February 14 fire was accidental and may have been caused by a cigarette. The agents \"also established that there was negligence and violation of the law on the part of authorities by allowing these prisons to remain overcrowded and in dangerous conditions,\" said US Ambassador Lisa Kubiske. The ATF experts carried out the investigation one week after the blaze following a request from Honduran authorities. \"The cause of the fire is believed to have been an open flame (the source of which could include, but is not limited to, a cigarette, a lighter, matches, etc.), although the actual ignition source was not recovered,\" the ATF team said earlier. The team said the \"tragic event has focused attention on inadequate safety practices within the Honduran prison system\" such as overcrowding and the presence of flammable materials. \"The United States urges swift action in devising and enacting necessary reforms to ensure the safety, health, and human rights of Honduran prisoners in order to prevent similar tragedies in the future,\" it said. The incident at the Comayagua jail was one of the world\'s deadliest prison blazes, and highlighted the problem of overcrowding in the region\'s jails. Meanwhile, some 200 relatives of the dead inmates marched in the capital Tegucigalpa Thursday chanting \"Justice, Justice!\" as they protested the delay in returning the bodies. It has nearly been a month since the fire \"and they have only delivered 110 bodies; we\'re not going to be waiting our whole lives,\" said Dennis Valladares, one of the march organizers. His 23 year-old brother Franklin Geovani died in the fire. Valladares was especially angry because his brother had completed his prison sentence in mid-December, but had not been released due to bureaucratic delays. President Porfirio Lobo named a committee of six ministers to assess the situation in the country\'s prisons and determine how to prevent mass deadly incidents in the future.