Indonesian police analyzed blood and DNA samples Thursday from unidentified body parts found inside the van that blew up outside Jakarta's Marriott Hotel (searchand a forensic chief said it was still unclear whether it was a homicide attack.

Officials said evidence abings.

In Jakarta (search), Brig. Gen. Dudon, the chief forensics specialist, said vital clues in the Marriott attack may have been washed away when firefighters used water to put out the blaze.

"Our work has been hampered by the fire brigade who tried to put out the fire, and also by the sprinkler system," he said.

Dudon said it was still not possible to determine whether the attack had been carried out by a homicide bomber. Several Indonesian officials had earlier said it may have been.

National police spokesman Lt. Col. Zainuri Lubis denied a media report that officers already knew the identity of the man believed to have been driving the vehicle that blew up Tuesday outside the Marriott Hotel in downtown Jakarta.

Investigators said they were using video evidence taken from the hotel's security cameras to see if they could help identify the driver of the vehicle.

Jakarta police spokesman Prasetyo (search), who like many Indonesians use only one name, said the driver could have detonated the bomb when approached by a security guard at the hotel.

"The car moved in and stopped (outside the lobby). A security guard approached the car and was getting closer when he noticed no one was getting out," said Prasetyo.

"Then it suddenly exploded."

At least 10 people were killed and 150 injured in the attack. In the confused aftermath, the Indonesian Red Cross put the death toll at 14.

"I can only confirm that we are trying to analyze DNA and blood samples found inside the vehicle," Lubis said.

On Wednesday, police released a composite sketch of a man who may have been behind the wheel. A second sketch, showing the reconstructed face of a severed head found at the scene, is expected to be released late Thursday.

Suspicion is strengthening that Jemaah Islamiyah (search), the Al Qaeda linked group blamed for last year's Bali (searchbombings, was also behind the Marriott attack.

In the first verdict of the Bali case, an Indonesian court on Thursday convicted and sentenced to death Amrozi bin Nurhasyim for his role in the attack that killed 202 people.

Amrozi was found guilty of planning and helping execute the bombings.

The Marriott blast was a bloody reminder of the threat of terror in the world's most populous Muslim nation, which had won plaudits for its investigation into the Bali bombings.

Maj. Gen. Made Pastika, who led the Bali investigation, said Thursday that in both cases attackers used mobile phones to detonate car bombs. Also like the perpetrators of the Bali bombers, the Marriott attackers used both TNT and RDX explosives, he said.

In addition, police said the bombers in both cases sanded down the chassis numbers on their respective vehicles in an attempt to shield their identities.

"The threat is still there and we have to increase our security," Pastika told reporters in Bali.

Both Australia and Indonesian have warned of more terrorist attacks, saying the trials of Jemaah Islamiyah members were reason enough for Muslim extremists to lash out.

A U.S. official in Washington said on condition of anonymity that the hotel blast had the hallmarks of previous attacks by Jemaah Islamiyah, whose alleged goal is to set up a pan-Islamic state in Southeast Asia.

Neighboring Australia has urged its citizens to defer travel to Indonesia and, if there, consider leaving.

"There could be a further terrorist attack in the next week or so and it's very important that people take that warning seriously," Foreign Minister Alexander Downer told reporters. "The 17th of August is Indonesia's National Day and that is a day when we think it's possible there could be a terrorist attack in the central Jakarta area."