( CNN ) -- Troops in the southern Philippines early Sunday took advantage of martial law to hunt down those believed responsible for last week 's killings there . President Gloria Macapagal Arroyo declared martial law in the southern province of Maguindanao after 57 people were killed in politically motivated violence . Maj. Randolph Cabangbang , deputy of operations for the Eastern Mindanao command , told CNN on Saturday that searchers have made arrests and recovered firearms and vehicles from a clan implicated in the killings . He said local residents welcome the deployment of the troops . `` We need this because we do not want those who perpetrated the crime to slip out of the province . And we may be having a hard time catching them , '' he said . Army spokesman Lt. Col. Romeo Brawner Jr. said martial law -- under which police can make arrests without a warrant -- went into effect at 9 p.m. Congress would have to approve any extension beyond 60 days . Brawner said the measure was invoked to impose peace on the region after the unrest , which led to troops being mobilized . `` Life is to resume normally and martial law is established to prevent new violence , with troops on the ground monitoring any possible violence breakout , '' he said . `` But the civilian government will be running the affairs of the province , not a military governor . '' Military police have detained three brothers and their father on suspicion of involvement in the unrest : Akmad Ampatuan , the vice governor of Maguindanao ; Anwar Ampatuan , the mayor of Sherif Auguak , Maguindanao 's capital ; and Zaldy Ampatuan , governor of the Autonomous Region of Muslim Mindanao . Andal Ampatuan Sr. , the patriarch , became ill and was hospitalized after he , too , was taken in . `` Local government will function , it will prevent armed groups from wreaking havoc ... and it will allow the officials search and find the guilty parties , '' Brawner said . Security forces on Friday searched the home of Andal Ampatuan Jr. , mayor of Datu Unsay and son of the provincial governor of Maguindanao , according to Brawner . Authorities say Andal Ampatuan Jr. directed the Nov. 23 politically motivated killings . Weapons were found in the house , Brawner said . On Tuesday , Philippine authorities charged Ampatuan and other suspects with 25 counts of murder in the killings . Still more suspects were taken into custody Friday . The Philippine military is investigating its own forces in connection with the case as well , Brawner said . The National Bureau of Investigation has moved a third witness to Manila for questioning , the Philippines News Agency reported Thursday . `` At the moment , we are interviewing the witness so that we would know what he knows about the incident in Maguindanao , '' NBI Director Nestor Mantaring said . The witness claimed to have been at the site during the massacre . `` He is very vital , '' Mantaring said . `` From what I know ... he knows a lot of information regarding the incident . '' Among the victims in the massacre were the wife and sister of political candidate Ismael `` Toto '' Mangudadatu , who had sent the women to file paperwork allowing him to run for governor of Maguindanao . He said he had received threats from allies of Gov . Andal Ampatuan , the father of the accused mayor , saying he would be kidnapped if he filed the papers himself . Witnesses and local officials have blamed the younger Ampatuan , a longtime ally of the Philippines president and a known warlord . They said the killings were an attempt to block Mangudadatu from challenging him in the May gubernatorial election . Also killed were a dozen journalists who had accompanied the women . Group : Philippines most dangerous country for journalists . Asked why martial law was imposed 12 days after the killings , Cabangbang said authorities `` were trying to build a case -- a tight case '' against suspects . `` But it is taking long to build a case , so I think the government gave us a free hand in arresting those who are suspects , and allowed us to search , even without warrant . So we really need this declaration of state of martial law . '' Violence in the run-up to elections is not uncommon in the Philippines . The Maguindanao massacre , however , is the worst politically motivated violence in recent Philippine history , according to state media . Maguindanao is part of an autonomous region in predominantly Muslim Mindanao , which was set up in the 1990s to quell armed uprisings by people seeking an independent Muslim homeland in the predominantly Christian Asian nation . Suspicion fell on Ampatuan after a government construction vehicle was found at the hastily dug mass grave that held the bodies of the massacre victims . CNN 's Talia Kayali contributed to this report .
Searchers make arrests , recover arms from a clan implicated in massacre . Martial law follows killings of a dozen last week in the Autonomous Region . Several members of powerful Philippine political family detained . Andal Ampatuan Jr. Mayor Datu Unsay directed killings , authorities say .