MANILA, Philippines -- Police officials on Friday dismissed speculations that a homemade bomb found in Taguig City was intended for the visiting wife of US Deputy Secretary of State John Negroponte.

The device, which explosive experts safety disarmed, was found by two child scavengers inside a styrofoam container outside the National Food Authority complex on DBP Avenue, more than a kilometer away from a charity housing project visited Thursday morning by Diane Negroponte, said Southern Police District director Chief Superintendent Roberto Rosales.

In an interview, Rosales pointed out that the explosive was discovered only on Thursday afternoon and was set to go off at 4:30 p.m., more than five hours after Negroponte had left the vicinity.

"You have to consider the time frame,” Rosales said. “Mrs. Negroponte was at the FTI Complex from 8 to 10 a.m., but the bomb was discovered only in the afternoon."

Manila hosted a meeting of foreign ministers of the ASEAN Regional Forum (ARF), attended by Negroponte and many other top officials. The visiting dignitary was at the Habitat for Humanity site in FTI Complex to help build low-cost homes in Taguig City.

Explosive experts disarmed the device, which consisted of a cellphone as a triggering device and ammonium nitrate as the explosive.

Taguig City police chief Superintendent Alfred Corpus said two boys aged 12 and 13 who were scavenging for garbage when they saw the styrofoam container. At 4:30 p.m., the childne heard a ringing sound, prompting them to open the package.

Inside were a cell phone, some valves and wires, a battery pack and a 355-ml plastic bottle containing ammonium nitrate.

Rosales said ammonium nitrate is a material used in illegal fishing, adding that "if this is the work of terrorists, they wouldn't use ammonium nitrate."

The panicked children then reported the find to authorities, and members of the explosive and ordnance division (EOD) later blasted the bomb on the site.

But initial reports from the EOD said the bomb could have not exploded because "there was something faulty in the assembly."

Corpus described the device as "an amateur job" and the material used was "a low explosive."

"If it went off, it would have only made a small hole in the ground ... It would not even [dented] the perimeter fence of the NFA," he explained.

Rosales meanwhile said investigators were looking into the possibility that the explosive might be connected to some internal issues or management problems at the NFA.

"We have talked to the NFA, they told us they don't have any crisis or problems with their people. Maybe there are some disgruntled quarters," Rosales said.

Corpus has already ordered stricter security measures to be implemented in vital installations in Taguig City.

"We will also strengthen our security operations like Oplan Sita and our checkpoints system," Corpus said, adding that they have not yet received any threats prior to Thursday's incident. With a report from Agence France-Presse