The improvised bomb detonated in Davao City which killed 14 people and wounded at least 70 last Friday likely came from central Mindanao and could be the handiwork of former students of Zulkifli Bin Hir alias Marwan, a Malaysian terrorist slain in a costly police operation in Mamasapano town, Maguindanao last year.

Philippine National Police Director General Ronald Dela Rosa said Wednesday said the bomb had the trademark of other bombs used by Bangsamoro Islamic Freedom Fighters, Ansar Kalifa and other terrorist groups in Central Mindanao.

"What we are looking here is the trademark or signature of other groups there," Dela Rosa told reporters in an ambush interview in Camp Crame.

In Davao City, a police special investigation task group released a computerized sketch of one of the suspects.

The man, wearing a black mask, left the bag which contained the bomb, according to witnesses.

The bomb was fashioned out of an 81 and 60 millimeter mortars tied with a wire."It was meant to explode together. The bombers' intention was to cause maximum casualty," said Dela Rosa..

Investigators are reconciling testimonies of witnesses to find out if there are three or four bombers. It was earlier reported the bombers are composed of two women and two men while others say the suspects are two women and one man.

Asked why the bombers could be Marwan's students, Dela Rosa said they have received information the Malaysian trained local terrorists before he was killed by Special Action Force commandos in Mamasapano last year.

"Those types of bombs can be traced back to Central Mindanao area Marwan trained a lot of people," said Dela Rosa.

"It's difficult to point on the exact group but definitely we can say the signature is from central Mindanao," he said.

Dela Rosa is also not discounting the possibility the bombs, which based on the their information are being sold by terrorists, could have been purchased by drug lords who are reeling from the effects of the government'a anti-drug war. Emmanuel Tupas