GOVERNMENT agents are looking at a possible terrorist link in the bombings in two Mindanao provinces on Dec. 22, Justice Secretary Menardo I. Guevarra said on Wednesday.

The National Bureau of Investigation (NBI) submitted a preliminary report on the Cotabato and Maguindanao bombings to the Justice department last week, “but the initial findings were still inconclusive,” he said in a Viber group message.

“They are presently conducting further investigation to determine if the perpetrators had any link with known terrorist groups operating in Mindanao,” Mr. Guevarra said. A progress report was expected this month.

“The NBI complied with my directive to submit a report before the year-end. Unfortunately, they have not identified the perpetrators as yet,” he said.

The Justice chief said government agents have another month to complete their probe and submit a final report.

Law enforcers earlier beefed up security in parts of the Mindanao region after blasts injured at least 21 people in Cotabato province on the eve of President Rodrigo R. Duterte’s planned visit on Dec. 23.

The initial explosions took place in Tantawan and Quezon Avenue in Cotabato City — the seat of the new Bangsamoro Autonomous Region in Muslim Mindanao — before 6 p.m. on Dec. 22. Two more followed in Libungan town in Cotabato province, and another in North Upi, Maguindanao province.

Authorities found another improvised bomb and detonated it on Monday morning, according to he Philippine Army.

The military said seven of those hurt were part of a military group that was helping to secure the area for a land distribution ceremony that Mr. Duterte was supposed to attend. Cotabato City is the seat of the new Bangsamoro Autonomous Region in Muslim Mindanao.

Seven other civilians were also reported hurt.

In Libungan, the first explosion took place near the town hall and the other at a store selling liquefied petroleum gas.

A 60mm mortar was used in the first and second blasts in Libungan, according to a bomb team. — Vann Marlo M. Villegas