Pimentel said the NBI should take over the investigation of the embarrassing incident to erase suspicions that police probers are out to whitewash the incident.
Marohombsar escaped the detention cell of the National Anti-Kidnapping Task Force (NAKTAF) on June 18 along with his alleged cohort Abdul Macaumpang and fellow inmate Rolando Patiño.
Pimentel stressed the people should be assured of an impartial and transparent probe as no less than incoming PNP chief Deputy Director General Hermogenes Ebdane Jr. said that the escape of Marohombsar was an "inside job."
"We are quite shocked by Ebdane’s allegation because what he was saying was Marohombsar could not have bolted jail without the help of some PNP officers and men," Pimentel said.
Pimentel noted that investigators should not ignore Marohombsar’s claim that he knew certain police officers who allegedly connived with and protected kidnapping syndicates in Mindanao.
"Was Marohombsar allowed to escape for fear that the Pentagon Gang leader might squeal on their alleged links with kidnappers?" the senator asked.
Pimentel recalled that before Marohombsar was captured by NAKTAF agents in Quiapo, Manila last March, he claimed he was planning to surrender to authorities and to reveal everything he knew about the kidnapping activities of Pentagon and other syndicates.
The Pentagon Gang itself is suspected of having been protected by ranking police officers in Mindanao.
In February, the PNP command dissolved Task Force Sanlahi, created by PNP chief Director General Leandro Mendoza to combat kidnapping in Mindanao, after two of its ranking officers were allegedly protecting syndicates in Southern and Central Mindanao.
The task force, which used to be headed by PNP Intelligence Group director Chief Superintendent Jaime Caringal, was dissolved shortly after a Bicol congressman donated some P2 million to help the unit in its anti-kidnapping operations.
Task Force Sanlahi was replaced with Task Force Mindanao, headed by Chief Superintendent Eduardo Matillano and based at Camp Lira in General Santos City.
Pimentel said the Marohombsar probe should not stop at the dismissal and prosecution of the 24 officers and men of the PNP Special Action Force who were guarding Marohombsar and two other inmates before they escaped on June 19.
"Marohombsar and his two companions were able to slip out of the supposedly well-guarded NAKTAF detention center at Camp Crame because of serious lapses in security. What investigators must determine is why the security measures failed and who should be held accountable for the fiasco," he said.
Pimentel said the investigation should also look into the possibility that Ebdane’s rivals might have had a hand in the escape to discredit him and foil his takeover as PNP chief.
On the other hand, he said the shameful incident gave Ebdane a "blackeye" because it happened right inside his turf, the NAKTAF.
"The escape of Marohombsar and the two other suspects is a big blow to the PNP. Unless it is solved and the culprits identified and punished, it will be a stigma to the police organization that is difficult to erase," Pimentel said.