Those taken in for questioning were identified as Candelaria Ortiz Tantoco, allegedly a lesbian who also serves as part-time driver of Blanca; Noel de la Paz, a distant relative of the victim; a certain Elena and two others who were not identified.
At least 12 people, among them Blanca’s driver Antonio Borja, have been grilled in connection with the killing. The others include Blanca’s colleagues at the Movie and Television Review and Classification Board (MTRCB).
Tantoco reportedly admitted driving the actress to the Casino Filipino in Parañaque City on Tuesday night, but refused to talk any further.
For his part, De la Paz claimed he was asked to check on Tantoco at the casino as Blanca’s husband Rod Lauren and other close relatives started worrying after she failed to come home early.
Director Nestorio Gualberto, chief of the Philippine National Police Criminal Investigation and Detection Group (PNP-CIDG) and concurrent head of "Task Force Marsha" formed specifically to investigate the murder, said nothing significant came out of their interrogation of Borja.
"He appeared to be just inventing his allegations and had only succeeded in giving us (raw) information, all non-relevant to the case," Gualberto said.
Borja earlier told the police that he knew of somebody who harbored ill-feelings towards Blanca — Dorothy Jones — in real life, and has the capability to do her harm.
Gualberto said Tantoco had been with the victim for several years, adding she may know some personal matters which could help solve the case.
National Bureau of Investigation Director Reynaldo Wycoco admitted it would be difficult to solve the murder as the killers left no fingerprints or any trace that they were present at the crime scene.
"There were indications that the crime was not spontaneous but planned. The killers left no trace of fingerprints which could help us track them down," Wycoco noted.
He hastened to deny, however, that they were facing a blank wall. "It’s not a blank wall...we are pursuing several leads which we could not divulge to the media for fear that it would jeopardize subsequent operations," Wycoco stressed.
"Our investigation into this case is in full-swing and on a 24-hour basis," Gualberto said.
Meanwhile, the police are also tracing the drivers and owners of at least 58 vehicles that entered and left the parking lots of Atlanta Centre on Annapolis street in Greenhills, San Juan from 5 p.m. Tuesday, the time Blanca supposedly left the MTRCB office on the 33rd floor, and 8:30 a.m. Wednesday when her body was discovered inside her green Nissan car while parked on the sixth floor.
"The security guard (of Atlanta Centre) jotted down the license plates of all the cars at the time she supposedly left the building and the time she was found dead," an investigator said.
Probers said Blanca reported for work as board member of the MTRCB the day before her corpse was found.
An examination of her remains showed she had dinner before her death.
"If she really had dinner prior to the killing, then being an actress, somebody could have had recognized her and could help identify her companions," the investigator said.
The probers were particularly interested in knowing why the security guard’s logbook showed the actress’ car left Atlanta Centre sometime on Tuesday night, but did not indicate the time it returned.
The investigators theorized that Blanca went down from the MTRCB offices to the parking space where she was apparently picked up by her assailants.
The probers said their investigation was being focused on the five-hour time frame when she must have been killed.
"What will she do at the parking lot of Atlanta Towers for five hours. Definitely, she came out of the building, either in her car or somebody had picked her up," the source said.
The casino logbook stated that the actress and her companions reportedly occupied Table 11, and played from 9 p.m. to 10 p.m.
The CIDG has requested the casino for a copy of the security video recordings, particularly those showing Blanca’s group.
"Hopefully, the tape could help us solve the case," Gualberto said.
De la Paz told police he was able to trace her at the casino on that fateful night.
The probers also batted for a new autopsy on Blanca’s remains to determine if she was sexually molested before she was murdered.
"Our medico legal expert appeared to have forgotten to examine the reproductive system of the victim. She was a woman of beauty and gentleness. That is precisely why we are not ruling out a crime of passion in this case," an investigator said.
Chief Superintendent George Aliño, director of the Eastern Police District (EPD) which is also helping in the investigation, said they are looking into other possible motives for the murder.
"We are still considering angles like robbery hold-up and personal grudge. We are still on the stage of evaluation that could lead us into specific angles that could possibly result in a solution of the case," Aliño said.
The multi-awarded actress sustained 13 stab wounds, mostly in the head, neck and body.
"While most of the wounds were superficial, the fatal one was at her throat with a pointed instrument coming from the left, cutting through right and hitting the jugular vein," chief medico-legal officer Superintendent Edgardo Guico said.
Guico noted that at least two types of pointed instruments, probably knives, were used in the attack because the wounds were not identical.
In another development, the Sandiganbayan hearing corruption charges against ousted President Joseph Estrada failed to resolve an urgent motion asking the court to allow him and his son Jinggoy Estrada to visit the wake of Blanca at the Christ the King Church in Green Meadows, Quezon City.
In filing the motion, lawyer Cleofe Verzola expressed optimism that the court would grant their request for humanitarian reasons, saying Blanca was a close associate and contemporary of her clients.
She expressed disappointment and dismay over the court’s failure to rule on her petition., saying the court should have considered the urgency of the issue. — With reports from Christina Mendez, Cecille Suerte Felipe, Non Alquitran, Marichu Villanueva