The escapees were identified as William Osoteo, Arvic Valentino, Raul Guimba, Alex Panida and Jojo Punzalan.
The prisoners escaped as they were being transported to the Medium Security Compound from the NBP hospital at around 7 p.m. One of them attacked prison guard Crisencio Mendoza, 45, with a knife.
The guard, who sustained a stab wound in the right chest, is still under observation at the Muntinlupa Medical Center.
His fellow guards Michael Garcia and Ernesto Aquino were unhurt.
Muntinlupa police chief Superintendent Jose Mario Espino said 10 inmates had initially been taken to the prison hospital. One was ordered confined while the rest were to be returned to their cells.
"The inmates and escorts were on board a multi-cab ambulance and were 100 meters away from the Medium Security Compound when one of the inmates suddenly stabbed Mendoza. The five inmates managed to escape during the commotion," Espino said.
The police chief said he has dispatched teams to track down the five escapees.
"Search operations are being intensified in Barangays Tunasan and Daang-Hari, particularly within the vicinity of the Victoria Homes Subdivision," he said.
Espino said they are requesting NBP officials to provide them cartographic sketches of the escapees.
Bureau of Corrections (BuCor) Director Vicente Vinarao said the dispatch of the inmates to the NBP hospital was unauthorized.
In a two-page memorandum to Justice Secretary Raul Gonzalez, Vinarao noted that 10 medium security inmates were dispatched by the shift commander of the Medium Security Camp without proper referral from the dispensary and without a proper ratio of security personnel, which was "in blatant violation of office rules and regulations."
"The mandatory ratio should have been 1 to 2. However, in this case, there were only three guards escorting 10 inmates, who were not even handcuffed and were not even in their proper prison uniforms. Apparently, there was a gross violation of the standard operating procedure relative to the guarding and escorting of inmates," he said.
The shift commander identified as a certain Inspector R. de los Santos, together with prison guards Mendoza, Aquino and Garcia will be slapped with charges of gross misconduct and infidelity in the custody of prisoners.
"Bringing the said inmates out and into to the hospital was illegal. In fact, only one of them was genuinely ill while the nine were just playing sick," Vinarao said.
He added that a flash alarm has been issued to all police units while a recovery team has been dispatched to conduct search operations.
Evasion of service of sentence charges will be filed against the five escapees, who had been convicted of car theft and homicide.
Meanwhile, Senator Manny Villar, who heads the committee on public order and illegal drugs, said that with the NBP incident, there is a need to implement reforms in the jail system.
"It is alarming to note that jailbreaks, whether successful or not, are getting frequent and in most cases they are a result of laxity and security measures and other operational loopholes. We should thoroughly review jail management procedures and retrain personnel on security procedures," he said.