Two weeks after a huge explosion destroyed a part of a chic shopping mall and killed 11 people in Philippines' financial hub, authorities have yet to give a definite and convincing conclusion of what caused the explosion.

Philippine police said this weekend that the explosion was most probably caused by a methane gas build-up and a spark from a running down electrical system at the underground of the mall, which is situated at the heart of the financial and business showcase of Makati City.

Police said they had recovered some pieces of evidence from the rubble of the explosion, including some circuit breaker and a centrifugal pump which was used to send water to the huge complex of Glorietta 2 Mall, but they are still looking for "a key piece of the puzzle" for concluding that it is a gas explosion and not a bomb as was originally thought.

The police statement was immediately supported by the government. Executive Secretary Eduardo Ermita said on Friday that the government was relieved it was not a terrorist attack as such an attack would harm the country's economy.

Glorietta 2 Mall is a highly popular shopping center for local and foreign customers and is located at the heart of the Makati financial district and close to several international standard hotels.

While 11 people were confirmed killed, more than 100 were injured in the explosion, the deadliest since a super-ferry was bombed in February 2004 at the Manila Bay in which more than 100 people were killed.

The police theory on gas explosion has been disputed by or caused skepticism from many people, including the Makati City Hall and business circle, while Ayala Land Inc., owner and operator of Glorietta 2, rejected it directly.

The influential Makati Business Club said independent panel should be set up to investigate the explosion. The mayor of Makati City, Jejomar Binay, has criticized police for "trending" the results of the investigation by speculating on a gas explosion while a key part of evidence has yet to be found.

Jaime Ayala, president and chief executive officer of the Ayala Land Inc., said at a press conference on Sunday that no evidence was found to indicate that the underground part of the mall was contaminated with a "volatile liquid" such as methane.

Ayala said the company's findings disputing the police's methane gas theory is being supported by a British scientist who is a specialist on wastewater and effluent treatment.

Police said it will take days before it could make public its final report on the mall explosion, along with reports by Australian, US and Israeli experts who the police said have helped investigate the explosion and have reached similar conclusions with the police.

Director Geary Barias, chief of the National Capital Region Command of the Philippine National Police, said it will take "one to two weeks more for lab results, autopsy report" to come out.

(Xinhua News Agency November 5, 2007)