Police in India's financial capital, Bombay, have detained hundreds of people in connection with the blasts that hit the city's train network, but no one has been arrested or charged. The attacks have also provoked an angry exchange between India and Pakistan.
After a massive overnight operation in Bombay, police said Thursday they have questioned hundreds of people who might have information about the culprits behind the bombs on seven commuter trains.
A senior police officer Sanjay Yadav says "known offenders and criminals" have been rounded up to verify if they have any connection with the blasts.
The detentions came as a man claiming to represent al-Qaida called a news agency based in Indian Kashmir to say that the terror network had set up a wing in the insurgency-wracked Himalayan territory. He praised the blasts in Bombay, saying they were triggered by India's oppression of minorities and Muslims.
The Indian army said it is evaluating the claim.
As investigators in Bombay searched for leads, the Indian Cabinet adopted a resolution expressing the government's determination to wipe out terrorism and apprehend those behind the attacks.
The attacks have triggered an exchange of barbs between India and Pakistan after two years of restraint as the rival nations have engaged in a peace process.
Within hours of the bombings, Pakistan strongly condemned the deadly blasts, and India did not link Islamabad to the attacks.
But India's hackles were raised by a comment attributed to Pakistani Foreign Minister Khursheed Mehmood Kasuri that the two countries could only cooperate to fight extremism if they resolve outstanding disputes such as Kashmir.
On Wednesday, Indian Foreign Ministry spokesman Navtej Sarna, issued a strong objection.
"We find it appalling that Foreign Minister Kasuri should seek to link this blatant and inhuman act of terror against men, women and children to the so-called lack of resolution of disputes between India and Pakistan," Sarna said.
New Delhi called on Pakistan to live up its pledge to take action against militants operating from its territory. Mr. Kasuri later told reporters in Washington that Islamabad is too often a victim of careless "finger-pointing", and it is not fair to assume that everything that happens in India starts in Pakistan.
Analysts say the Bombay attacks will test the peace process, which has helped to lower tensions between the rivals, but has brought them no closer to solving their dispute over Kashmir, which both countries claim.
In the past India has accused Pakistan of supporting Muslim militant groups waging a separatist insurgency in Indian Kashmir. Islamabad strongly denies doing so, and says it is playing a front-line role in the global war against terror.
