MANILA -- President Gloria Macapagal-Arroyo ordered an immediate investigation on the pre-dawn bombing attacks in Mandaluyong City and Quezon City Monday.

Press Undersecretary Anthony Golez said the Philippine National Police (PNP) has been tasked to “come up with a swift investigation” on the blast, which fortunately did not hurt anyone.

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“These are all going to be investigated on as swiftly as possible and we are expecting the PNP to submit report to the President as soon as possible,” Golez said.

An explosion rocked San Miguel Corporation building in Julia Vargas Avenue and San Miguel Avenue in Mandaluyong City around 3 a.m. Monday, while another explosion happened at Puregold Supermarket along Commonwealth Avenue in Quezon City around 5 a.m.

Golez said the authorities are still looking into the possible connection of the two blasts.

He, however, believed that the incidents are isolated cases and there is no reason for the public to be alarmed.

“What we can see based on the reports that these explosions are (caused by) just like pillbox type (explosive). We do not know the motivation of this. This is just an isolated drug related activity. Drug-related, meaning maybe there was a man high in drugs who did it,” he said.

He also said the explosions have nothing to do with politics.

Golez added that there was no need to place Metro Manila on heightened alert because of the blast incidents, since the PNP is on top of the situation with regard to peace and order in the metropolis and elsewhere.

He also denied that the blasts have something to do with the two-day visit of US Secretary of State Hillary Clinton to the country.

Clinton is set to arrive in Manila on Thursday to meet up with President Arroyo and to hold consultations on issues concerning the Philippines and the US.

National Capital Region Police Office (NCRPO) director Roberto Rosales, meanwhile, said the explosion may have been caused by a pillbox, a type of crude bomb.

In the Quezon City blast, Rosales said a security guard identified as Darwin Taringding saw a man threw a plastic bag containing the explosive then ran off, leaving his shoes behind as he hurried away.

The NCRPO chief said that when Taringding approached the bag, it exploded suddenly and smoke enveloped him.

Police are also eyeing possible labor problems between the management of Puregold and its employees.

Authorities have earlier ramped up security measures in the metropolis with the deployment of additional foot and mobile patrols to deter crimes during the Holiday season.

Police had also conducted several joint simulated exercises with security guards of shopping malls and other business establishments as part of the improved security plan.

On October 30, two pre-dawn blast rocked Quezon and Pasig cities on the day Metro Manila police were to go on full alert for the All Saints' and All Souls’ Day weekend.

The first blast occurred at 1:05 a.m. in front of the Burgundy Tower along Katipunan Avenue in Quezon City.

It created a crater and damaged a parked Honda Civic belonging to Ateneo student Allan Valencia.

A second explosion occurred shortly after the Quezon City incident, where another IED exploded across the Union Bank Plaza along Meralco Avenue in Pasig City. (Jill Beltran/AH/Sunnex)