Five years into the incident, the police could not end the investigation of the bomb blast that killed seven people and injured several others.

"Some young workers joined the party in a plan to attack or create panic," a CID official said, asking not to be named. "The attackers went underground. We raided some houses to arrest them but found they used false names and addresses," the official said.

The CPB leaders alleged the police leaked information to two suspects helping them escape arrest. The deadly explosion still remains in mystery that the CPB blames on the lack of determination of the government to nab the criminals.

CPB President Manzurul Ahsan Khan recalled the tragic episode: the bomb ripped through a crowd on January 20, 2001, about 180 metres from the dais that seated leaders of 10 political groups. He believes the device was detonated by remote control.

Investigators say the CID is now determined to correct all past flaws in the investigation, including failure to collect material evidence from the scene, conduct the inquiry on the basis of unbiased witness account and nab the real attackers.

Police arrested 13 people, 11 of them were released on bail, CID officials said. "The release of the accused made the case fragile," an official said, requesting anonymity.

At least 119 people have been killed and over 600 injured in 13 explosions in public places since March 1999, but no attackers were brought to justice.

"Bomb blasts have become commonplace experience, but nobody seems to care," said Arifur Rahman, a resident of Mohammadpur.

"The police investigate the blasts but investigation reports have never been published. It makes us believe the probe reveals links of influential people to the incidents," said Ruhum Hasan Prince, a CPB central committee member.

A judicial commission, headed by Justice Abdul Bari, submitted its initial probe report to the home ministry, which was scheduled to be forwarded to the higher authorities. But the report is still pending with the ministry.

Home ministry and senior CID officials said they have a bar to talk about the issue.

The police and other agencies mostly ignore forensic experts, who could play a role in investigation of bomb blasts.

Examining the dead, a forensic expert can say whether the bomb was carried in or thrown from outside. They can also say who was nearest to the bomb and what he was doing at the time, experts and doctors said.

In most foreign countries, the police immediately secure the area, invite forensic experts to see the spot, collect strewn evidence and take pictures of the area before clearing the area for police and evacuation of the bodies, experts said.

The scenario is different in Bangladesh. After such fatal incidents, people reach the spot before police or experts, evacuate the dead and injured and unknowingly destroy evidence.