A joint investigation team comprising members of different detective agencies, Rapid Action Battalion and the police on Sunday night picked up two persons on suspicion of having links to the Habiganj carnage.

Former president of Habiganj unit Chhatra Shibir Nurunnabi Uzzal was held from his house at Habiganj while Dorga ward Chhatra Dal President Jamal alias Kala Jamal from Shubidbazar at Sylhet.

Intelligence sources said that the two were not arrested formally, they were detained and interrogated on suspicion. Both of them fit the description of suspects given by witnesses.

Jamaat leaders of Habiganj, meanwhile, were putting pressure on the investigators to release the Shibir leader, added the sources.

A police source said the detainees could get released any time as the pressure on them (police) to free the two was mounting.

Police said that not only the two, they would pick whoever they suspect of having connection with the carnage. They would keep constant watch on the suspects.

Investigators said that Uzzal and Jamal had denied their involvement in the carnage.

An investigation source said the investigators basing on the eyewitness accounts are scouring the areas for up to four persons including the two, who, the witnesses said, sped off the scene on a motorbike shortly after the blasts. They went in the direction of Habiganj sadar.

"But we are cautious in considering whether the witnesses had fed us wrong information or how much of what they said was true," he added.

The investigators had raided across a wide area in greater Sylhet on the basis of leads provided by the witnesses. At the same time they are verifying the authenticity of the witnesses' accounts.

They however could not arrest anyone till Sunday night.

A number of intelligence and police officials on condition of anonymity said that several activists and criminals allegedly belonging to the BNP and Jamaat might have been involved in the grenade blasts. The raids and interrogations are being done in line with this assumption.

"In any investigation many things might appear suspicious and many people can be suspected and detained for questioning," said an official. "We have detained the two as suspects and it's a very primary step. No one can say it for sure that they did it (blasts) or Shibir or Chhatra Dal was involved in it."

Another source said that the intelligence men are reviewing whether criminals from outside of the greater Sylhet region were involved in the carnage. They are also trying to find out who had helped the grenade throwers in Habiganj -- especially in Bangaon village that stands adjacent to Baidderbazar.

"Former finance minister and local lawmaker on the AL ticket SAMS Kibria was the prime target in the grenade attack," said an intelligence official, "We set about the investigation by looking for the answer to the question -- who gains most from his death?"

The investigators also looked for internal feud in Awami League or presence of rival factions. "But we found nothing to corroborate that intra-party feud led to the grisly crime," added the official.

Presence of any 'ambitious leader or group' in the local AL to challenge Kibria was not evident as well to the investigators.

Besides, the investigators examined other possibilities and beneficiaries of Kibria's death. They found that the slain lawmaker was widely accepted as a 'good person' throughout his constituency. His image made it difficult for the candidates of other parties to win the next election from this constituency. If he is killed, a major hurdle can be easily overcome for his political opponents and it might also be the motive for the murder, investigators say.

"We are considering every possibility and ruling out nothing. But right now, our analysis shows that the local BNP leaders are most benefited from Kibria's death," said an official.

"The possibility of the Jamaat's winning the constituency is lower than that of BNP. But Jamaat may have long-term benefits. And that is why, they come second on the list of suspects," he added.

Besides the investigators are looking into whether any third force had hired criminals affiliated with a section of Jamaat or BNP to throw the grenades.

While talking to The Daily Star, Habiganj BNP President Aminur Rashid Emran denied outright any of the four-party alliance member's connection with the carnage. He also ruled out internal conflict in Awami League as the reason for the killing.

"I don't think Awami League has done it, " Emran added.

"But if anyone can present acceptable proof that some of our party men were involved -- even if that points the finger at me -- our party will take steps," Emran said.

He said, "I believe a foreign interest group did it through their (Bangladeshi) accomplices. I also think the attack was carried out by the outsiders."

However, a veteran BNP leader of Habiganj seeking anonymity said, "Money and muscle dominate the ruling parties' politics in Habiganj. The victory of BNP in the municipality election through massive rigging has created resentment within the party itself.

"

"It's not possible for BNP or Jamaat to be involved in this grenade attack. But one cannot rule out presence of such a clique within BNP and Jamaat that might have done it!" he added.