MANILA, Philippines - Security forces are pressing ahead with the hunt for those behind a massacre of 57 people despite President Arroyo's scrapping of martial law in the region, an aide said Sunday.

"While rebellion was stopped, the military's mopping-up operations are ongoing, such as hunting for those who should be hunted," Arroyo spokesman Cerge Remonde said.

"As for evidence gathered during the rebellion, it will be used in filing rebellion charges... this is also true for evidence in the multiple murder charges," Remonde told government radio.

Arroyo on Saturday lifted martial law in the southern province of Maguindanao, where the election-linked massacre occurred on November 23, after an eight-day clampdown that netted more than 500 suspects.

Martial rule was imposed in the country's second-poorest province to allow arrests without court orders, helping police detain members of a powerful political clan led by former Maguindanao governor Andal Ampatuan Sr,, Arroyo's former political ally.

His son, Datu Unsay Mayor Andal Ampatuan Jr. has been arrested and charged with multiple counts of murder for allegedly ordering the kidnapping and shooting of the 57 people, including journalists and relatives of a local rival.

The Ampatuans were later expelled from Arroyo's ruling coalition and the clan patriarch was among 24 people arrested and separately charged with rebellion after martial law took effect.

The government also seized a vast array of weaponry from the Ampatuans' large group of bodyguards.

Some 4,000 troops will remain in Maguindanao while security checkpoints will stay in place on roads, military officials said.

However, police will now need court orders to arrest suspects or search private property for weapons or other evidence in the massacre and rebellion cases.

Opponents and rights activists accused Arroyo of imposing martial law as a pretext to allow her to stay in power beyond a presidential election scheduled for May 2010.