**Philippine officials have arrested a powerful official in Maguindanao and imposed martial law in the province after the massacre of 57 people there.**Andal Ampatuan Sr was arrested at dawn, officials said, along with another senior member of the powerful clan.
Andal Ampatuan Sr’s son, Andal Ampatuan Jr, turned himself in last week and was charged with 25 counts of murder.
The move comes after troops raided compounds belonging to the family and found an arsenal of buried weapons.
Prosecutors have issued subpoenas to six members of the Ampatuan family, including Andal Ampatuan Sr, to appear at a hearing on 18 December.
They deny any involvement in the 23 November attack on a political rival’s convoy and have not yet been charged.
Among the 57 victims were members of a rival clan and 30 journalists.
Weapons cache
The Ampatuan clan have long controlled Maguindanao province and have been loyal supporters of President Gloria Arroyo.
Since the killings, Mr Ampatuan Sr, his son and his brother Zalday have been expelled from her party.
Friday’s raids followed the discovery of what a military spokesman described as an arsenal of weapons buried several hundred of metres outside the Ampatuan compound in Maguindanao’s capital, Shariff Aguak.
“We estimate that these weapons are enough to arm a battalion [500 soldiers],” national police chief Jesus Verzosa said.
An investigation has been ordered into how the military weapons ended up in the hands of the Ampatuans.
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.