Police said the body of Zairudin Manindeg was the latest to be discovered among the three suspects who were all believed to have been summarily executed.
Another suspect, Ariel Macapaar, a member of the Iranon tribe, was shot dead by still unidentified gunmen in a farming village in nearby Matanog town, less than a week after the bombing.
His brother, Khalid was among those arrested by the police last Monday. Two other suspects identified as Kusain Taha and a certain Omar are now under police custody.
Authorities are still verifying the identity of a still unidentified man whose body was recovered last week in a remote area. Local officials said the body matched witnesses’ descriptions of one of the suspects in the bombing.
Local officials believe the three had been killed by relatives of the blast victims to settle a "blood debt."
Most of the victims reportedly belong to the influential Iranon clans, known for their "rido," or exacting vengeance for the killing of any family member.
At least 22 people were killed and 71 were wounded when a bomb blast ripped through a packed sports hall here on Jan. 4.
The bomb was apparently intended to kill town Mayor Vivencio Bataga, authorities said.
One of those killed was Salman Macarambang, son of the re-electionist vice mayor of Barira town also in Maguindanao.
Bataga, a former Army colonel seeking re-election in the May polls, survived at least three attempts on his life last year. Bataga had blamed his political rivals for the attacks.
Bataga yesterday issued an appeal against resorting to retaliations to allow police to finish the investigation and identify the real culprits in the bombing.
"Violence cannot quell violence. We have to give the police and the military enough time to put all the suspects behind bars for them to be prosecuted to the fullest extent of law," Bataga said.
Authorities are still on the manhunt for Parang Councilor Abdul Katab and Suharto Ahmad, the alleged masterminds of the bombing.
Ahmad reportedly owned the bomb-laden motorcycle used in the bombing of the packed gymnasium.