MANILA — A blast occurred at the New Bilibid Prison's maximum security compound in Muntinlupa on Friday morning, police said.

Authorities were demolishing "kubols" or villas when the blast happened at around 10 a.m., said Metro Manila police chief Maj. Gen. Guillermo Eleazar.

Pieces of an improvised explosive device (IED), 2 hand grenades, and a blasting cap were found in the area, he said.

It was not immediately clear whether or not the blast was intentional. There was no immediate report of casualties.

Bureau of Corrections chief Gerald Bantag was directed to "submit a written report and to commence investigation," said Justice Secretary Menardo Guevarra.

Bantag took charge of BuCor last month after his predecessor, Nicanor Faeldon, was fired by President Rodrigo Duterte, over alleged anomalies in the early release of heinous crime convicts.

-- Report from Jerome Lantin, ABS-CBN News