The National Bureau of Investigation (NBI) is looking into illegal drug trade as a possible link to the killing of Tanauan City Mayor Antonio Halili last Monday, Justice Secretary Menardo Guevarra said on Wednesday.

Guevarra also ordered the NBI to investigate Tuesday's ambush of General Tinio Mayor Ferdinand Bote as he left the National Irrigation Administration office in Cabanatuan City. Bote, according to the Philippine National Police (PNP), has no links with illegal drugs.

"Yes, the NBI will look into that (drug) angle. The NBI is expected to look at all possible angles and motives," Guevarra said in an interview.

The PNP, which started its probe of the Halili shooting ahead of the NBI, is also looking at the same angle.

The NBI sent agents to Tanauan City and met with several city hall officials to gather information.

Halili, who paraded suspected drug dealers through the streets. was shot dead during the weekly flag-raising ceremony.

But President Rodrigo Duterte called this a front by Halili and accused him of involvement in illegal drugs. DMS