MANILA, Philippines? (UPDATE) Authorities are looking at three possible angles in the explosion that rocked Metro Manila on Tuesday, with Interior and Local Government Secretary Jesse Robredo saying that one of the possible motives was a destabilization move against the government.

Robredo, in an interview after the local peace and council meeting in Pasay City on Wednesday, said that other angles being studied are terrorism and a diversionary move to withdraw public attention from the incidents of car theft-related murders in recent days.

"It's possible that we're being led away but what's clear is that whoever is responsible for this knows what he's doing and this is not the work of an ordinary person," Robredo added.

The official also said that the 81-millimeter mortar used in the blast was primarily used in Mindanao.

"But as of now it's too early to say about any exact motive behind the blast," Robredo said.

Police have stepped up security after the explosion, even as Robredo assured the public that the government is doing everything to prevent similar incidents from occurring again.

Earlier, Robredo directed the PNP to get to the bottom of the bombing and called it a ?well-planned, deliberate act to kill innocent people and to sow fear among the civilian populace.?

With a report from Alcuin Papa, Philippine Daily Inquirer