"They are from the same school. We found similar materials, similar tools, a similar method. That's their job, that's the same network, they are JI."
At least nine people were killed and more than 50 injured when near simultaneous explosions tore through the Ritz-Carlton and JW Marriott hotels on Friday.
Besides the Bali attacks, JI has been blamed for several other high-profile attacks in Southeast Asia in the past decade, including another bombing against the JW Marriott in Jakarta almost exactly six years ago.
According to investigators, the bombers stayed in Room 1808 of the Marriott for two nights before the attacks and disguised themselves as guests when they walked into crowded dining and meeting areas and detonated their suitcase devices in the two hotels.
Al Jazeera's Step Vaessen, reporting from Jakarta, said police were getting a clearer picture of the intended target of the bombing, pointing to a high-level business breakfast meeting at the Marriott.
The meeting occurred every Friday at the same time and place and witnesses said the bomber headed straight for the meeting where he killed many business leaders.
Ansyaad Mbai, the Indonesian security ministry's anti-terror desk chief, said evidence pointed to Noordin Mohammed Top as the mastermind of the attack.
Manhunt for Noordin
Police were hunting for Noordin, a fugitive Malaysian master bomb-maker, who was a key member of JI before he broke away after an alleged falling-out with the leadership over the targeting of civilians.
He is accused of masterminding bombings at the Marriott in 2003, the Australian embassy in 2004 and Bali restaurants in 2005 which killed more than 40 people.
|Forensic teams continue to sift through the scene of the blasts for evidence [Reuters]
Mbai said the advanced skills and planning used to pull off the blasts at the hotels, said to be the most tightly guarded buildings in Indonesia, were extremely disturbing.
"Their new skills and advanced tactics, enabling them to smuggle the explosives into the targeted site, pose a very serious threat for our country," he told the AFP news agency.
Investigators have been examining body parts and other forensic evidence in an attempt to identify the two bombers, one of whom local media and analysts say is believed to be Nur Hasbi, who has been linked to Noordin.
On Sunday, people gathered outside the Ritz-Carlton by a makeshift memorial for the victims.
Four foreigners were identified as being among the nine dead in the bomb blasts.
Stephen Smith, the Australian foreign minister, visited the site of the attacks on Sunday, as his government warned that more attacks were possible in a travel advisory that urged Australians to reconsider travelling to Indonesia.