Philippine authorities, under intense public pressure to make arrests in the country's worst election massacre, said Wednesday they are investigating a member of a powerful clan allied with the government along with four police commanders. Officials recovered 11 more bodies Wednesday - six in a large pit buried alongside three vehicles and five in a mass grave - bringing the death toll in Monday's attack on an election caravan to 57, including 18 journalists. The military also announced it will disarm two government-armed civilian militia companies, or about 200 men, in southern Maguindanao province, which is ruled by the powerful Ampatuan clan. The militia are meant to act as an auxiliary force to the military and police in fighting rebels and criminals but often serve as a private security force of local warlords. All the firearms, ammunition, equipment and uniforms of the militiamen are to be turned over to the army's 6th Infantry Division, armed forces spokesman Lt. Col. Romeo Brawner said. He said the military also has revoked all its permits to carry firearms in Maguindanao and Sultan Kudarat, the two provinces now under a state of emergency. No suspects have been formally named in the killings, which provoked outrage beyond the Philippines, with UN Secretary-General Ban Ki-moon and media and human rights watchdogs calling on President Gloria Macapagal Arroyo to swiftly punish the attackers. In a statement, the US Embassy in Manila condemned the killings. “Such barbaric acts violate the most fundamental principles of human rights and democracy,” Ambassador Kristie Kenney said. Arroyo vowed justice for the victims and declared a national day of mourning for them. “This is a supreme act of inhumanity that is a blight on our nation,” she said in a statement. “The perpetrators will not escape justice. The law will haunt them until they are caught.” The bodies were found sprawled a few miles (kilometers) off the main highway in southern Maguindanao province on a remote hilltop, and in three nearby mass graves. The vehicles – a sedan and two vans –- were crushed by a large backhoe that ran over and buried them, crime investigator Jose Garcia said. Police were trying to determine whether the vehicles were part of the caravan. The dead included the wife and two sisters of gubernatorial candidate Ismael Mangudadatu and 18 Filipino journalists who were accompanying the caravan to file his election papers. It is the highest number of reporters killed in a single attack anywhere in the world, according to media groups.