Investigators subsequently found evidence of suitcases with improvised explosive devices (IEDs) and flammable material, including three undetonated IEDs. Inside one of the suitcases containing the undetonated IEDs, a digital timer encased in transparent plastic was packed alongside a dozen plastic bottles containing fuel oils and chemicals. After the bombings, eight unaffected carriages were allowed to continue onwards to Lahore with passengers.
Both the Indian and Pakistani governments condemned the attack, and officials on both sides speculated that the perpetrators intended to disrupt improving relations between the two nations, since the attack came just a day before Pakistani Foreign Minister Khurshid Mahmud Kasuri was to arrive in New Delhi to resume peace talks with Indian leaders. There have been a number of breaks in the investigation of the bombings, but as of May 2008, nobody has been charged for the crime.
In recent years, the Indian and Pakistani governments have made attempts to bring peace or to at least calm the tensions between the countries. One such attempt in the peace process came with launch of the Samjhauta Express, so-named because the word samjhauta means "accord" and "compromise" in Hindi and Urdu, the national languages of India and Pakistan, respectively. This twice-weekly train service runs between Delhi and Attari in India and Wagah and Lahore in Pakistan. Launched in 1976, the Samjhauta Express served as the only rail connection between the two countries until the launch of the Thar Express. Given the nature of the transnational service and the ongoing violence in the region, the Samjhauta Express was always heavily guarded, as it was a high-risk target for terrorist attacks. Weeks after the Indian Parliament terrorist attack on 13 December 2001, the train service was discontinued amid security concerns. Although it resumed service on 15 January 2004, the train was placed on high security. Just days before the attack, Pakistani Foreign Minister Khurshid Mahmud Kasuri announced that he was going to Delhi on 21 February 2007 to meet with Indian government officials to continue peace talks and to sign a nuclear risk reduction agreement.
It was about 11.52 when I showed the signal lantern to the Attari [Samjhauta] Express which was coming in very fast, probably at over 100 kilometers an hour (62.1 mph). Just as reached near the home signal, I could hear two loud explosions from the coaches near the guards' van at the rear.
After the explosions, both carriages were engulfed in flames and many passengers were incapacitated by the smoke. Witnesses claim to have seen passengers screaming and attempting to escape, but since most of the train's windows were barred for security reasons, many could not escape in time. The injured were pulled out of the burning carriages and onto the track by fellow passengers and local residents.
In the end, the terrorist attack left 68 people dead and 50 injured. Most of the dead and injured were Pakistani nationals, though some Indians, including railway workers, were also killed. Initial identification of the victims was hindered by the fact that many of the bodies were charred beyond recognition. The rest of the train, which was left undamaged by the attack, continued on to the border town of Attari, before being transferred to a Pakistani train that took passengers to their destination in Lahore.
Indian Minister of Railways, Lalu Prasad Yadav, condemned the incident and went on to say that the attack was "an attempt to derail the improving relationship between India and Pakistan." He also announced compensation payments of Rs. 10,00,000 (approx. €17,500 or US$22,750) for the next-of-kin of each of the deceased and Rs. 50,000 for those injured. Home Minister Shivraj Patil claimed that "whoever is behind the incident is against peace and wants to spoil our growing relationship with other countries". Prime Minister Manmohan Singh expressed "anguish and grief" at the loss of life, and vowed that the culprits would be caught. India's foreign ministry also promised to issue visas for Pakistani relatives of those killed or injured in the blasts. Indian journalist Siddharth Varadarajan argued that the peace process should stay on track and that any wavering would be tantamount to surrendering to terrorism.
The opposition Bharatiya Janata Party condemned the attacks and petitioned the ruling Indian National Congress to ask Pakistan to comply with its 2004 promise to crack down on cross-border terrorism. The party also argued for a harsher anti-terror bill to take a "zero tolerance" approach to terrorism in India.
The Bush administration condemned those responsible for the bomb explosions aboard the Samjhauta Express. On behalf of the United States government, White House spokesman David Almacy stated:
We express our deepest sorrow for this tragedy and extend condolences to the families of the victims. We appreciate the leadership of Indian Prime Minister (Manmohan) Singh and Pakistani President (Pervez) Musharraf, and condemn those who seek to undermine the progress in relations between the two countries.
In early March, Haryana police arrested two people from the city of Indore who allegedly sold the suitcases used in the bombings. No charges were pressed on the individuals. A probe conducted by the commissioner of Railway Safety officially determined that the explosions and fire on the Samjhauta Express had been caused by bombs located in the upper compartments in coaches GS 03431 and GS 14857. The probe also showed that the train slowed down to a speed of just before it was going to pass the Diwana train station. The results strengthened the belief that the suspects got off the train before the explosions. On 31 March, a 25-year-old man was interrogated after being arrested in Amritsar after jumping off a moving train under suspicious circumstances.
No major developments have taken place in the investigation since late March 2007. Meanwhile, the Indian and Pakistan governments have agreed a bilateral pact to extend passenger train and freight services between the two countries until 2010. In late April, the Indian and Pakistan governments initiated steps for safety and security measures for the Samjhauta Express. The two countries started sharing information on passengers travelling on the trains. The train is now under a reservation system, and as one Railway Ministry source said, "[w]ith no unreserved coaches, we now have complete passenger details from their ticket reservation data a few hours prior to their boarding, and departure of the train. Also in late April, three new coaches equipped with India's most advanced fire fighting systems were added to the Samjhauta Express. Indian Railway Ministry sources commented that the system acts with brake pressure, and this glass-encased system could throw water up to . Indian and Pakistani members of the Anti-Terror Mechanism (ATM) group met on 22 October 2007 to update each other regarding the status of the investigation.