TAGUM CITY, Philippines -- Police and military authorities here remain clueless on what caused the huge explosion that occurred near a military camp and two provincial jail complexes in a village here Tuesday night.

Investigators are still determining whether the blast was caused by an explosive device or a grenade since there was no trace of bomb or grenade fragments in the vicinity where the explosion was heard, said Senior Superintendent Benilito Bianzon, Davao del Norte police director.

The explosion, Bianzon said, was heard at around 10:45 p.m. amid a heavy downpour in the vicinity of the Davao del Norte provincial rehabilitation center (DPRC) gate and the bunkhouses of the Division Recon Company of the 1003rd Infantry (Raptor) Brigade in the village of Mankilam.

"Our EOD (explosives and ordnance disposal) team went there to investigate but they have yet to locate the exact site of the explosion which probably may be manifested by a small crater in the ground," Bianzon told reporters on Wednesday.

The military also said it could not yet determine what really exploded as they were relying also on the findings of the police EOD.