By Rachel Harvey
South-east Asia correspondent, BBC News
Ismael Mangudadatu's wife, sisters and many supporters were killed on Monday
A mayor in the southern Philippines, whose wife was among 57 people killed in an ambush, has filed nomination papers to run for governor.
A key suspect in the massacre, Andal Ampatuan Jnr, has surrendered to the authorities.
Investigators believe the killings were politically motivated, ahead of the 2010 provincial and national elections.
Meanwhile the Philippine Justice Secretary has been giving more details of the evidence gathered so far.
The mayor, Ismael Mangudadatu, travelled with a police and army escort along the same road where his wife, sisters, and at least 27 journalists were killed.
Mr Mangudadatu has now officially registered his candidacy for next year's elections - the task his relatives were so brutally prevented from completing on Monday.
"Only death can stop me from running," he said.
Justice Secretary Agnes Devanadera told local television that some of the gunmen detained after the attack had implicated the man now being treated as the chief suspect, Andal Amaptuan Jr.
Mr Ampatuan is being held in custody in the Philippine capital Manila. He denies any involvement in the killings.
Several other people are being investigated including the police chief of Maguindanao, the southern province where the killings took place.