Security forces on Saturday arrested Maguindanao Gov. Andal Ampatuan Sr. for his alleged involvement in the massacre of 57 people in the province last November 23.

The arrest was made right before President Gloria Macapagal Arroyo's expected declaration of martial law in Maguindanao.

A radio report said Ampatuan Sr. will be brought by security forces to hospital before being actually detained.

The report said the governor was arrested by Task Force Alpha, a task group created by police to conduct operations in connections with the massacre.

The governor's son, Datu Unsay Mayor Andal Ampatuan Sr., is currently detained at the National Bureau of Investigation in Manila. He has been charged with 25 counts of murder.