MANILA : Philippine police have placed Metro Manila on red alert after a powerful explosion rocked a crowded shopping mall in the business district.

Eight people were killed and close to 70 others injured.

Police sources have been quoted as saying traces of C4 explosives were found at the scene, but investigators are still trying to determine the cause of the blast.

It was the jam-packed lunch hour when an explosion ripped through an upscale mall right in the heart of Makati, Manila's financial district.

Damage to infrastructure was massive, and a passageway linking the Glorietta 2 mall to another shopping centre was totally destroyed.

The powerful blast also shattered windows and damaged several cars parked just outside the building and witnesses reported that a portion of the ceiling collapsed.

"The man in front of me who was wearing blue died. We don't know what happened to his child but his wife's foot was severely injured," said one eyewitness.

As soon as the police and ambulances arrived, the wounded were carried out of the mall in stretchers.

Many of the victims had been hurt by shards of glass.

The police initially attributed the explosion to a gas leak in a restaurant at the mall, but later expanded the possible causes.

Gerry Barias, Metro Manila Police Chief, Philippine National Police, said: "I told the media earlier that the cause of the explosion was Liquefied Petroleum Gas but that wasn't an official assessment. We're not discounting any other possibilities."

Before the blast, the police had received intelligence reports of plans by terrorists to launch attacks right after the Muslim holy month of Ramadan.

Bomb squads are sifting through the debris looking for clues, while more police officers have been activated to divert traffic and seal off the surrounding area. - CNA/ch