Another bomb was found in southern Philippine province of North Cotabato early Wednesday, local media reported.
A report by GMA TV said authorities were able to prevent the bomb from exploding.
The new explosive found at the Makilala municipal hall was similar to the one detonated on Tuesday night near the Makilala plaza, which killed 12 people and wounded 29 others.
Following the discovery of the bomb, the Philippine National Police (PNP) on Wednesday morning placed its forces in Mindanao and the Philippine capital of Metro Manila under full alert.
Besides the explosion in Makilala on Tuesday, another bomb also went off in a market in Tacurong City in the province of Sultan Kudarat hours earlier, wounding six people.
The United States and Australia issued travel advisories against the Philippines on the same day when the explosions occurred.
In a statement posted on its website, the U.S. Embassy in Manila said it received "credible information" of an imminent attack in central Mindanao "over the next several days."
Source: Xinhua