MANILA, Philippines?Manila Police District investigators will subject five security guards of the Harrison Plaza mall to a lie-detector test following revelations made by a security official at the shopping complex that last Tuesday morning?s robbery may have been an inside job.

Theft and robbery section head Chief Insp. Edgardo Carpio stressed that the five security guards of the Kemen Security Agency whom he refused to identify by name were not yet considered suspects in the robbery.

?We are investigating all possible angles,? Carpio said, adding that the security guards were to undergo the polygraph test on Friday or Monday.

Apart from the security guards at the establishment, investigators have also questioned workers doing repair work inside the Harrison Plaza in Malate.

Carpio said the police was encountering difficulties in the investigation because the mall?s management has not been coordinating with the authorities.

?That is why we are going to them to determine if they are still interested in filing a complaint. Until now, they (mall management officials) have not gone to us,? Carpio said, pointing out that the mall has not even declared how much was lost in the robbery.

On Tuesday, at around 1:00 a.m. some 15 heavily armed men aboard a government vehicle (SFN-529) ransacked for two hours the Velco Finance Department on the 2nd floor of the mall and took an undetermined amount of cash and other valuables from a vault.

Apart from the cash, the robbers also took some 15 handheld radios, seven handguns and several mobile phones from the mall.

The suspects who were reportedly all wearing helmets usually used by cops, face masks, vests and shirts with ?BITAG? markings, proceeded to the security office of the mall before going to the finance office.

Alfaraz Ledesma Ong, detachment commander of the Kemen Security Agency, told investigators that the heist could have been an inside job, with the robbers knowing all the locations of the offices inside the mall.