Extra troops have been moved into Maguindanao province
The Philippines is to pull the entire police force from a southern province where 57 people were massacred.
Interior Secretary Ronaldo Puno said the 1,092 police officers of Maguindanao province would be replaced by personnel from other regions.
Mr Puno said the move was to ensure an impartial investigation of the murders.
A local mayor, who belongs to a powerful clan in the province, has been charged with multiple counts of murder over the 23 November killings.
The accused, Andal Ampatuan Jr, has denied the charges.
"We are replacing those that have been there for a long time and may be perceived to be partial to one side or the other," said Mr Puno.
Regional police superintendant Bienvenido Latag said the Ampatuan family might have relatives among the province's police force who could try to sabotage the investigation.
Those killed were trying to file nomination papers for Ismael Mangudadatu, who was mounting a challenge to Mr Ampatuan in next year's gubernatorial elections.
Andal Ampatuan Jr (right) is accused of ordering and leading the killings
The group included Mr Mangudadatu's wife, his two sisters, other supporters and 30 local journalists.
They were ambushed by a group of about 100 armed men - allegedly led by Mr Ampatuan - and taken to a remote hill region and shot at close range. Their bodies were then dumped in shallow graves.
Elections in the Philippines are often hit by violence but this incident has horrified the nation.
President Gloria Arroyo has promised that the killers will be brought to justice. The Ampatuans are close supporters of Mrs Arroyo, but since the murders several family members have been removed from her party.
Several members of the Ampatuan family, including the patriarch Andal Ampatuan Sr, are under investigation as well as some members of Maguindanao's police force.
Two militiamen connected to the Ampatuans have been arrested. The gun belonging to one - Esmail Canapia - matched bullet casings found at the massacre site, police said.
The government has armed militias in the south to act as an auxiliary force to the army and police battling insurgents but they often end up as the private armies of local strongmen.