Passport details of Pakistani nationals travelling by the Samjhauta Express in which explosions killed 66 people near Panipat on Sunday have been sent to Islamabad for verification, the government said Monday.

A number of Pakistani nationals have been killed in the incident, many charred beyond recognition, an external affairs ministry spokesperson said.

However, the exact number of Pakistanis killed was not yet clear as identification is going on, ministry spokesperson Navtej Sarna told reporters.

A team of Pakistan High Commission officials has reached Panipat to help in the identification process.

"Unfortunately, we do not have the break-up of passengers. It is very difficult to ascertain the number of Pakistanis. The entire process is being carried out with the help of Pakistani authorities," Sarna said. He said efforts are underway to identify the injured.

The government of India is making all arrangements for travel of passengers who have reached Attari, Sarna said.

Two officials of Pakistan Railways are also expected to reach Atari to assist in the process.

Noting that explosions had occurred on the train, the MEA spokesman said the Indian government "strongly condemns" the blasts.

"The government will make every effort to bring to justice the perpetrators of this heinous act... We also convey our heartfelt condolences to the victims of this gruesome tragedy," Sarna said.

"The causes of the incident are being investigated," he said, adding the main focus at the present was on dealing with the humanitarian consequences of the incident.

Refusing to react to Pakistan Foreign Office spokesperson Tasnim Aslam's reported comment that security of the Pakistani passengers was India's responsibility, Sarna said attention was at present on providing succour to the victims.

Coverage: The Sanjhauta Express blasts