Muntinlupa police chief Senior Superintendent Roberto Rongavilla identified the suspect as Samsudih Mokalid, a native of Maguindanao and a resident of Signal Village, Taguig.
He was arrested by police three hours after an improvised grenade went off at around 8:30 p.m. at a tiangge on Montillano street.
Police are blaming a long-time feud between two groups of Muslim vendors as the likely cause of the attack.
Rongavilla said the blast took place as Maguindanaoan and Maranao vendors were fighting over leadership of the Muslim Vendors Association.
"As the two groups were arguing an explosion rocked the tiange area near a convenience store on Montillano street.
Eighteen people, mostly Muslims, were wounded," Rongavilla said. He added that a flea market stood on a private lot in the area where the grenade was planted.
Suffering shrapnel wounds were Gonting Sankupan, Nora Sankupan, Madid Khalid, Ragdaing Sabdulah, Abdulahhab Parhan, Pangaga Saripuda, Maute Jampar, Lawa Panda, Kalib Magdani, Jadjara Sankupan, Akmad Sirid, Mark Lao, Arnais Reyes, Janeth Ramos, Oscar Vargas, Antolin Villasista, Raquel Taylan and Reynaldo de Jesus, a traffic aide.
They were taken to the Ospital ng Muntinlupa for treatment. As of press time, four have been released from the hospital.
Southern Police District (SPD) director Chief Superintendent Wilfredo Garcia said Mokalid was apprehended inside the Kelly Compound in Alabang after witnesses tagged him as the man responsible for the blast.
Charges of multiple frustrated murder and illegal possession of firearms and explosives are now being readied against the suspect.
"Mokalid had accomplices and we are looking at five more suspects. We are conducting follow-up operations to arrest his companions," Garcia said during the presentation of Mokalid to mediamen at SPD headquarters in Taguig.
Crime scene investigators recovered from the blast site a lever from an old apple-type improvised grenade, iron balls, splinters, batteries and a caliber .38 revolver with five bullets.
The gun was found inside the bag of one of Mokalid’s cohorts who managed to escape. The latter left the bag after figuring in a scuffle with De Jesus.
Muntinlupa City Mayor Jaime Fresnedi ordered the city police to arrest all those responsible for the attack.
Meanwhile, two World War II grenades were recovered in Western Bicutan yesterday morning.
Garcia said a concerned citizen identified as 18-year-old Rominick Borral made a call at the police station saying old grenandes were found near Sitio Matatag street.
Members of the Explosives Ordnance Division, led by Senior Police Officer 3 Rodolfo Montaril, recovered two fragmentation grenades, which were without safety levers and pins.