Seven more persons of interest in the slaying of broadcaster "Percy Lapid" have been secured by the National Bureau of Investigation bringing to 15 the personalities being investigated, Justice Secretary Jesus Crispin Remulla disclosed Sunday.

The number of POIs increased as authorities also included those who have information on the mysterious death of Jun Globa Villamor inside the National Bilibid Prison.

The POIs are now under the custody of the NBI and Philippine National Police as of Saturday.

"We are talking to a number of people and many have been explaining. We have taken seven more into custody that possibly can shed light on the death of Villamor, that it is not an accident, not natural but a planned death," Remulla said.

The justice chief is confident that formal charges will be filed in connection with the killing of the broadcaster this week.

"The results are very satisfactory. I think we've made a lot of progress. I think that proper cases can be filed by the end of next week. Hopefully," Remulla said.

Remulla also disclosed that there are "two persons of interest as masterminds" in the sensational Lapid slay case.

The DoJ chief, however, refused to identify them as he doesn't want to preempt the ongoing investigation which is now entering its last phase.

"We have to determine everything and we do not want to violate the rights of anyone," Remulla said.

"The investigation is almost over. It is just a matter of filing the cases and probably being able to identify the masterminds," he pointed out.

The public was assured by Remulla that the identities of the masterminds will be revealed in the complaint that will be filed by the NBI and the PNP.

Last Saturday, forensic pathologist Dr. Raquel Fortun released the results of her independent autopsy on the body of Villamor.

Her autopsy showed that Villamor died of suffocation after a plastic bag was placed over his head.

"Based on available information regarding the circumstances surrounding the death, the manner is homicide," Fortun said in her report.