A powerful blast rocked a crowded shopping mall in Manila's financial district Friday, killing at least eight and injuring scores of others, and police said they were not ruling out a bomb attack.

The explosion caused extensive damage throughout the Glorietta 2 shopping complex in Makati, toppling roofs, destroying walls, and sending debris crashing onto cars outside.

At least eight people were killed and as many as 70 others were injured, said metropolitan Manila police chief Geary Barias.

"I was told by officials of the explosives and ordnance disposal division that it could be a bomb but it's not definite yet," said national police chief Avelino Razon.

Witnesses told radio stations they saw bloodied people being helped out and carried away in ambulances. An Associated Press photographer saw four bodies covered with blankets.

Taxi driver Mario Em said he had just dropped off two female passengers at the mall when the blast hurled the two women against his vehicle, killing them instantly.

He said he pulled one of the victims, who was pregnant, from underneath his car.

"The blast was so loud I lost hearing," he said.

Barias said an initial report suggested the blast was caused by a cooking gas tank in a mall restaurant. But hours later, he clarified the explosion was not inside the restaurant but at the entrance of the mall and police were investigating the cause.

"It's too early to say if it's terrorism related," Barias said.

Police and the military in the Philippine capital declared the highest state of alert, and President Gloria Macapagal Arroyo said in a statement she was "deeply saddened" by the incident and ordered police to investigate "and to leave no stone unturned."

Al-Qaeda-linked militants, who have waged a yearslong bloody bombing campaign in the southern Philippines, have targeted Manila before.

In 2004, Abu Sayyaf militants, notorious for kidnappings and beheadings, blew up a passenger ferry in Manila Bay, killing 116 people in the country's worst terrorist attack. The following year, four people were killed and dozens wounded when a bomb exploded on a Makati bus and two southern cities.

Several months ago, authorities were alerted to an alleged terror plot to plant bombs in Manila's business districts of Makati and Ortigas, said a government counterterrorism official, speaking on condition of anonymity because he was not authorized to speak to the media.

People inside the mall scampered toward the exits when the blast shook the mall.

"One man who was in front of me was already dead. There was a child but we don't know where the child is now," said Dennis Inigo, who was shopping at the time of the explosion.

"The man's wife was with me a while ago, and her leg was shattered. Many people were falling on top of each other," he said. "It was loud, and then it became dusty."